Then folks who don't use tox can do `pip install -r
dev-requirements.txt`
Since this is pip, which created the idea of requirements files, it
seems nice for the project to have one to showcase the idea.
Also cleaned up the tox.ini and made it more compact (fits now on my
laptop screen) and consistent.
* Deprecates the --download-cache option & removes the download
cache code.
* Removes the in memory page cache on the index
* Uses CacheControl to cache all cacheable HTTP requests to the
filesystem.
* Properly handles CacheControl headers for unconditional
caching.
* Will use ETag and Last-Modified headers to attempt to do a
conditional HTTP request to speed up cache misses and turn
them into cache hits.
* Removes some concurrency unsafe code in the download cache
accesses.
* Uses a Cache-Control request header to limit the maximum
length of time a cache is valid for.
* Adds pip.appdirs to handle platform specific application
directories such as cache, config, data, etc.
We've had a number of problems with pytest-xdist, primarily on
Python 3.x where we had intermittent failure. However we're also
getting intermittent failures on Travis due to how long the tests
actually take to run. Given two different intermittent failures
it seems that the one that runs faster should be preferred.
* Better output with the bare asserts we use throughout the tests
* Function fixtures are pretty nice, especially as a way to
start a background server or create an isolated virtualenv
