Pirec

Changed
- Wheels are now built for Python 2 and 3.
- JSON pipeline report is now saved to report.json. This can be changed by
supplying the report_name keyword argument to Pipeline.run(). Fixing the name
makes automated reading data from the report later easier.
- Keyword arguments to recorded functions are now saved correctly.

Added
- Values returned from pipelines are now recorded.

Added
- A recorder that sends a message to Slack is now included.
- Multiple recorders may now be used.

Changed
- Printed output from commands is now stripped of whitespace before recording.

Added
- The command argument to call() is now recorded along with the output.

Added
- The pipeline record now includes information about the executing environment.
- Pipelines can now accept input arguments that are not subclasses of artefacts.Artefact.

Changed
- Fix docstring errors.
- Add more tests.
- Tidy up documentation structure.

Added
- The call() function now returns process output.