Feature: add --bail support for mocha

Add support for `--bail` flag for mocha tests

## Proposed usage(s): 

- `learn --bail`
- `learn -b`
- `learn test --bail`
- `learn test -b`

## Expected behavior 

See [mocha command line usage](https://mochajs.org/#command-line-usage)
'Abort ("bail") after first test failure'

Mimics usage of `--fail-fast`