adding in the necessary require statement (in nodejs).

Inspired by this issue : https://github.com/axios/axios/issues/792#issuecomment-289306590

The alternative way I added is more common and requested, as seen from issues
#362 , #350. Should be helpful for the beginners ( I was personally stuck for a bit too )

Also, added notes about using Async/Await with caution

- Adding information in README for socketPath when used with a proxy
- Adding an HTTP test for socketPath option

it seems when cancelling a post request we need to specify cancellation token as an axios parameter and not as a data item.

Since `async/await` is not widely used, and I have seen quite a few questions on how to actually use `async/await` with Axios, I figured it would be nice to have it in the readme, front and center.

* Adding a way to disable all proxy processing

When the proxy field in configuration is === false all proxy processing is
disabled. This specifically disable the 'http_proxy' environment variable
handling.

Fixes #635
Related to #434

* Change readme wording

From review comment on PR (#691)

Header names are lower cased by axios Which make sense since the header names are case insensitive.

It's missing an `)`

Change the links of the logos of different browsers according to the original repository.

Fixes #615