chore: update agent-js to latest

commit 7c5e71488df430b89de637a15b56814db196e752
Author: Islam El-Ashi <ielashi@users.noreply.github.com>
Date:   Sat Nov 7 00:30:05 2020 +0100

    feat: DER-encode public key and principal ID when using Plain Authentication. (#48)

    BREAKING CHANGE

    If a developer relies on the inner work of SenderPubKey or manually instanciate Principal, the API changed.

commit a254861ae4bfe608734c8c190e4033cfe39f047b
Author: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Date:   Fri Nov 6 15:17:32 2020 -0800

    chore(deps): bump node-fetch from 2.6.0 to 2.6.1 in /e2e/node (#49)

    Bumps [node-fetch](https://github.com/bitinn/node-fetch) from 2.6.0 to 2.6.1.
    - [Release notes](https://github.com/bitinn/node-fetch/releases)
    - [Changelog](https://github.com/node-fetch/node-fetch/blob/master/docs/CHANGELOG.md)
    - [Commits](node-fetch/node-fetch@v2.6.0...v2.6.1)

    Signed-off-by: dependabot[bot] <support@github.com>

    Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

commit 694849109bc28fea80119388504127e889b36d15
Author: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Date:   Fri Nov 6 15:17:14 2020 -0800

    chore(deps-dev): bump node-fetch from 2.6.0 to 2.6.1 in /packages/agent (#50)

    Bumps [node-fetch](https://github.com/bitinn/node-fetch) from 2.6.0 to 2.6.1.
    - [Release notes](https://github.com/bitinn/node-fetch/releases)
    - [Changelog](https://github.com/node-fetch/node-fetch/blob/master/docs/CHANGELOG.md)
    - [Commits](node-fetch/node-fetch@v2.6.0...v2.6.1)

    Signed-off-by: dependabot[bot] <support@github.com>

    Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

commit 88af47f79b5e9f3a5e08abbf0ce03b3140357fc0
Author: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Date:   Fri Nov 6 15:16:53 2020 -0800

    chore(deps-dev): bump node-fetch in /packages/bootstrap (#51)

    Bumps [node-fetch](https://github.com/bitinn/node-fetch) from 2.6.0 to 2.6.1.
    - [Release notes](https://github.com/bitinn/node-fetch/releases)
    - [Changelog](https://github.com/node-fetch/node-fetch/blob/master/docs/CHANGELOG.md)
    - [Commits](node-fetch/node-fetch@v2.6.0...v2.6.1)

    Signed-off-by: dependabot[bot] <support@github.com>

    Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

commit ba4b082e5795150176f7adad989c3613edceb85f
Author: Hans <hans@larsen.online>
Date:   Thu Nov 5 12:49:59 2020 -0800

    test: add ic-ref, ci e2e and lerna support to repo (#47)

    This refactors the repository to use lerna to manage its monorepo's packages. It also adds the e2e tests from the SDK repo that we previously had to remove. More e2e tests will be added later, but this unblocks working with DER and Identity work as we can now at least run some e2e tests now (instead of mocking the http connection).

commit 8baa1cfc227d003c2806df1057b92009159df250
Author: Hans <hans@larsen.online>
Date:   Tue Nov 3 11:04:36 2020 -0800

    feat: use anonymous principal by default in HttpAgent (#46)

    If the auth transform is missing and the principal is anonymous, use an
    anonymous auth transform. Otherwise, use the auth transform as normal.

    # BREAKING CHANGE
    Before, an auth transform would not be called if it was missing, now it
    results as an error if the principal is not anonymous. This was because
    just using the packet as is without putting it in an envelope was a bug
    and should never be sent to a replica anyway. Now this is explicit.

commit 1a714e6c53f5e467112b964b71204b6d2eb545ef
Author: Hans <hans@larsen.online>
Date:   Tue Nov 3 11:04:15 2020 -0800

    feat: add a getPrincipal() method to Agents (#40)

commit 324e856944adb7f79a2afa2cffbdb6d144b35ab4
Author: Hans <hans@larsen.online>
Date:   Tue Nov 3 08:49:44 2020 -0800

    feat: add the canister ID to the window.ic object (#41)

    This can be useful to know the canister ID of the current frontend.

commit 8680a2cf4994b45c6e00ffb0b5a12b379f5ff919
Author: Hans <hans@larsen.online>
Date:   Mon Nov 2 21:57:21 2020 -0800

    feat: add a cache bust hash at the end of javascript output (#39)

commit 9f2ed968b7cc9f4b854af5e23edca19d34124909
Author: Benjamin Goering <benjamin.goering@dfinity.org>
Date:   Tue Sep 22 15:28:49 2020 -0700

    docs: polish docs/npm-publish.md per @hansl feedback (#37)

    via: pr feedback on dfinity/agent-js#36

nix/sources.json

@@ -15,7 +15,7 @@
     "agent-js-monorepo": {
         "ref": "next",
         "repo": "ssh://git@github.com/dfinity-lab/agent-js",
-        "rev": "8f3b96a42a71ec7f34089ffd6d4eb8249076d229",
+        "rev": "7c5e71488df430b89de637a15b56814db196e752",
         "type": "git"
     },
     "bats-support": {