Looper

Added

- ability to use PEPs from PEPhub without downloading project [341](https://github.com/pepkit/looper/issues/341)
- ability to specify pipeline interfaces inside looper config [Looper Config](https://looper.databio.org/en/dev/how_to_define_looper_config/)
- divvy re-integrated in looper
- divvy inspect -p package
- Looper will now check that the command path provided in the pipeline interface is callable before submitting.


Changed
- initialization of generic pipeline interface available using subcommand `init-piface`
- `looper report` will now use pipestat to generate browsable HTML reports if pipestat is configured.
- looper now works with pipestat v0.5.0.
- Removed --toggle-key functionality.
- Allow for user to input single integer value for --sel-incl or --sel-excl

Fixed
- Fix regression for var_templates expansion.

Fixed
- Fix for expanding paths properly.

Added

- preliminary support for [pipestat](http://pipestat.databio.org).
- ability to skip samples using `-k` or `--skip` [367](https://github.com/pepkit/looper/pull/367)
- ability to input a range into `limit` and `skip`[367](https://github.com/pepkit/looper/pull/367)
- `limit` and `skip` are now both usable with Destroy and Run. [367](https://github.com/pepkit/looper/pull/367)
- ability to generate generic pipeline interface using `init -p` or `init --piface` [368](https://github.com/pepkit/looper/pull/368)
- Fixed ability to use custom sample index
- Added `write_custom_template`, a built-in pre-submit plugin for writing templates

Changed
- looper now returns nonzero if any samples fail submission
- various other developer changes

Deprecated
- `path` variable will be deprecated in favor of `var_templates` [322](https://github.com/pepkit/looper/issues/322)

Changed
- Fixed bug with use_2to3 for setuptools compatibility.