Fixes reading response data in multiple chunks

[vojtechhabarta]

This PR fixes problem with larger response from Jenkins API.
When response data are larger it is needed to read all chunks and join them before parsing the json (http://stackoverflow.com/questions/5083914/get-the-whole-response-body-when-the-response-is-chunked).

(BTW instead of request library I would recommend to use axios which uses Promise API, parses JSON by default and works well with TypeScript async/await.)

[alefragnani]

Hi @vojtechhabarta,

First of all, thanks for the PR. I didn't have this issue, but probably because my Jenkins jobs are simple, and didn't fire chunks. I'll test it and release an update ASAP.

About the axios library, I'll take a look later, testing it with other features that I intend to add to the extension. Thanks for your suggestion.