New status comment format (details of warnings, errors, test failures)

[czechboy0]

It would be great to report failed tests, errors and warnings in detail in the GitHub comments already.

Test failures: we receive in the integration object.
Warnings/errors: we need to make an extra call to the integration's /issues endpoint.

• required refactor + tests: Refactored comment creation (+ added tests) #184
• add object that constructs the new comments with input data
• pipe through the logic for asking for details of issues if build summary tells us that there was at least one error or warning)
• only report the most serious problem (e.g. don't report warnings when a test failure or error occured)
• split test (failure) information per device
• add which devices the tests ran on

Currently blocked by

• rdar://23142264 (Integrations endpoint doesn't return test result when asked for >1 integration)

[czechboy0]

Mentioned in #84, it would be better if Buildasaur gave more detail about the devices that ran tests, e.g.

Result of integration 1
Integration took 25 minutes and 46 seconds.
All 0 tests passed, but please fix 567 warnings on iPhone 6 Plus iOS 8.4
1800 tests passed and 2 failed, but please fix 567 warnings on iPhone 4s iOS 7.1
1800 tests passed and 2 failed, but please fix 567 warnings on iPhone 4s iOS 8.4