Percy

Improved CodeShip Pro support. (58)

- Improved supported for Circle 2.0 (45).
- `CIRCLE_WORKFLOW_WORKSPACE_ID` is now used as the parallel nonce if `PERCY_PARALLEL_NONCE` is not specified. This gives a better default higher-level grouping for snapshots when tests are parallelized in Circle, otherwise it has no effect. We believe this change is backwards compatible, but please reach out if you have issues.

- Removed deprecated PERCY_PROJECT handling. You can safely remove PERCY_PROJECT from CI environment variables.
- Backwards-incompatible change: the interface to `create_build` has changed slightly and now only accepts optional arguments. There are no other major changes or backwards-incompatibilities in this release.

Added:

- Add GitLab CI environment variable support

Removed:

- Python 3.3 support

Improve integration with Travis CI PR builds.

Get commit data from git if available, then fallback to ENV variables