Bloated projectile caches can cause freezing and delays. This is
especially so if you accidentally index $HOME or /, which will bloat
them into the hundreds of MBs.
+ Adds purging of blacklisted, over-sized and non-projects from
projectile's cache when Emacs is killed.
+ Projectile's project file cache will now expire after a week.
+ Corrects file paths in core/doctor's filesize checks.