* Cached objects are no longer shared between different clcache versions to
avoid restoring objects which were stored incorrectly in older clcache
versions.
* Feature: The cache statistics now count the number of calls with /Zi (which
causes debug information to be stored in separate `.pdb` files)
* Feature: a new `-c` switch is now recognized which can be used to clean the
cache. Cleaning the cache means trimming the cache to 90% of it's maximum
size by deleting the oldest object. Doing this explicitly avoids that this
happens automatically during a build.
* Feature: a new `-C` switch was added which can be used to clear the cache.
Clearing the cache removes all cached objects, but keeps all hit/miss
statistics.
* Improvement: The `ccache -s` output is now prettier.
* Improvement: cleaning outdated cache entries is now a lot faster
* Bugfix: Support use of py2exe with Python 3.4
* Bugfix: Support includes parsing when cl language is not English (GH 65)
* Bugfix: Fix bug causing statistics to get corrupted after concurrent invocations (GH 70).
* Bugfix: Invalid values passed via `-M` are now handle gracefully.
* Bugfix: The cache size and the number of cached entries is now updated
correctly after pruning outdated objects.
* Internal: major overhaul to the test infrastructure: a lot more tests are
now executed on each change, and they are executed automatically via
AppVeyor.
* Internal: a lot of issues (both cosmetic as well as semantic) reported by
pylint have been fixed. pylint is now also executed for each change to the
codebase via AppVeyor.