Byoc

Feature
* Cache parameter values ([`c320d9e`](https://github.com/kalekundert/appcli/commit/c320d9e56cfd01e965b6c48a2e68ff1496ff44c8))

Feature
* Allow multiple keys to be associated with a single config ([`556dfa4`](https://github.com/kalekundert/appcli/commit/556dfa420dff1b354f0d5f322d8b8a5747afb61a))
* Add a reload() function ([`5fdde1f`](https://github.com/kalekundert/appcli/commit/5fdde1f8221d31479a5b77685cf60ebe7a084904))
* Allow layer locations to be callables ([`ad5ad16`](https://github.com/kalekundert/appcli/commit/ad5ad16845da3ecebfe07ed5aa787634d560594c))
* Allow not_found() to take any iterable type ([`507c133`](https://github.com/kalekundert/appcli/commit/507c133ff0122dce45ccc0742cd166426c877daa))
* Print all docopt messages to stderr ([`3737b3a`](https://github.com/kalekundert/appcli/commit/3737b3af634aed54780a184679e3b69245fd1103))
* Export the lookup() function ([`9694681`](https://github.com/kalekundert/appcli/commit/9694681a33852005a48a6c609ba12af6bd56b213))
* Teach make_map() about elipses ([`9c11385`](https://github.com/kalekundert/appcli/commit/9c11385b5a6afed620d6d8ca847fba01dda5844d))
* Add ignore argument ([`476b114`](https://github.com/kalekundert/appcli/commit/476b11459a83e8d168c3000f14e88b9e1158a57f))

Fix
* Remove debug calls ([`04401f6`](https://github.com/kalekundert/appcli/commit/04401f649bb832cdd0c7829779dff684b1488783))

Feature
* Use classes for grouping; add CompositeConfig and CallbackConfig ([`751630f`](https://github.com/kalekundert/appcli/commit/751630fba26ff1c3ee63966f098886203efe2012))

Fix
* Exclude inactive layers when looking up parameter values ([`6b1433c`](https://github.com/kalekundert/appcli/commit/6b1433ca9765d6814043cd2092d7c8ee1a9ba8bf))

Feature
* Add ArgparseConfig ([`6594f3c`](https://github.com/kalekundert/appcli/commit/6594f3c99844825d285828ae37f3dbcc6cda05c7))

Documentation
* Add a brief description of the project ([`10e46e2`](https://github.com/kalekundert/appcli/commit/10e46e25f27c61e767dd252d9aa8cca177051ae5))