Simplify cargo installation

[anupdhml]

To install tremor-language-server 0.8.1 from crates.io, users have to configure cpu target as per https://github.com/simd-lite/simd-json#cpu-target (for the simd-json dependency that comes via tremor-script currently).

Example:

RUSTFLAGS="-C target-cpu=native" cargo install tremor-language-server

Needed configuration is there in the project .cargo:
https://github.com/wayfair-tremor/tremor-language-server/blob/v0.8.1/.cargo/config

But this file is not read during cargo install so it only works for builds straight from the git repo.

To simplify the installation process, this MR opts to use simd-json with allow-non-simd feature. Ease of installation is more important for tremor-language-server than json processing performance so this should be fine to do.

---

We had similar behavior in v0.7.4 but it got removed as part of 0.8 release here: c45b23c

Now we specify simd-json only as build-dependency. If we choose to add a allow-non-simd feature to tremor-script (pointing to the simd-json feature of the same name), we can revisit this MR (that might be better than adding a simd-json dependency here, which is not really used directly in trill).

---

Verified as working via:

cargo install --git https://github.com/wayfair-tremor/tremor-language-server.git --branch simplify_cargo_install

[codecov]

Codecov Report

Merging #49 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master     #49   +/-   ##
======================================
  Coverage    0.00%   0.00%           
======================================
  Files           7       7           
  Lines         296     296           
======================================
  Misses        296     296           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 438add7...7f5e336. Read the comment docs.

[darach]

LGTM