Features
* Index and package file list cache invalidation
* Set max disk-usage of cached files
* Support coloured logging when `coloredlogs` is installed
* Expose cache functionality
* All files from all indices for a package is returned, instead of just the first index the package was found in
* Any fragment in the original index is returned
* Any attributes in the original index is returned
Changes
* Change package structure: app is now at `proxpi.server.app`
* An exception during file-download will be raised instead of returning the original URL
* Environment variables have been renamed, and are now all prefixed with `PROXPI_`
* Debug-logging only enabled during testing and debugging: otherwise uses info-logging
Improvements
* Use `lxml` for HTML parsing: significant speed up in package-list from PyPI
* Added integration tests
* Cache isn't initialised unless `proxpi.server` is imported
* Cache initialisation happens asynchronously
* URLs are built in templates
* Index caches are thread-safe