internal: Fix caching issues with config variants. Before, changing config variant values could incorrectly re-use a previously cached config as long as there were the same number of variants. Now we build a stricter cache hash based on the actual values.

[pytest]
norecursedirs = .* _darcs CVS .svn .git .hg *.egg-info dist build bower_components node_modules venv tmp* _cache {args}