Add query parameters serialization(#29)

[alexkhismatulin]

Hey
I tried to keep this as minimalistic as possible. It uses UrlSearchParams under the hood so IE11 is not supported. Also, this means that it's not going to serialize nested objects properly. I added a paramsSerializer config parameter so it's going to be used when there's a need to serialize something more complex than a plain unnested object.

Closes #29

[googlebot]

We found a Contributor License Agreement for you (the sender of this pull request), but were unable to find agreements for all the commit author(s) or Co-authors. If you authored these, maybe you used a different email address in the git commits than was used to sign the CLA (login here to double check)? If these were authored by someone else, then they will need to sign a CLA as well, and confirm that they're okay with these being contributed to Google.
In order to pass this check, please resolve this problem and then comment @googlebot I fixed it.. If the bot doesn't comment, it means it doesn't think anything has changed.

ℹ️ Googlers: Go here for more info.

[alexkhismatulin]

@googlebot I fixed it.

[googlebot]

CLAs look good, thanks!

ℹ️ Googlers: Go here for more info.

[developit]

Good job with the tests. This one just needs to be golfed a little and then I think we'll be good to merge.

The size bot can't comment on fork PRs (yet), here's where we're at:

Size Change: +295 B (9%) 🔍

Total Size: 2.95 kB

Filename	Size	Change
dist/redaxios.js	965 B	+100 B (10%)	⚠️
dist/redaxios.module.js	965 B	+97 B (10%)	⚠️
dist/redaxios.umd.js	1.02 kB	+98 B (9%)	🔍