[WIP] Full BitBucket Support

[czechboy0]

Work on BitBucket is being merged into this branch.

Outstanding tasks:

• refresh token handling (BitBucket refresh token flow #222)
• refresh token handling tests with DVR (tested manually, but still should be unit tested)
• support for getting branches (can't find the API, doesn't seem possible)
• support for posting comments (BitBucket posting comments #223)
• conditional requests to save rate limit (no idea how, doesn't return ETag)
• getting the rate limit (no idea, X-Request-Count is all over the place)
• pagination (BitBucket pagination #224)

[buildasaur]

Result of Integration 1

Duration: 5 minutes and 37 seconds
Result: Perfect build! All 36 tests passed. 👍
Test Coverage: 24%

[buildasaur]

Result of Integration 2

Duration: 3 minutes and 51 seconds
Result: Perfect build! All 37 tests passed. 👍
Test Coverage: 26%

[buildasaur]

Result of Integration 3

Duration: 5 minutes and 20 seconds
Result: Build failed 1 test out of 42

[buildasaur]

Result of Integration 4

Duration: 4 minutes and 53 seconds
Result: Perfect build! All 41 tests passed. 👍
Test Coverage: 27%

[buildasaur]

Result of Integration 5

Duration: 4 minutes and 27 seconds
Result: Perfect build! All 41 tests passed. 👍
Test Coverage: 27%

[buildasaur]

Result of Integration 6

Duration: 5 minutes and 14 seconds
Result: Perfect build! All 41 tests passed. 👍
Test Coverage: 27%