Make grizzl optional dependency

Notice user if grizzl is set as completion system but not installed
Merge pull request #140 from ptrv/make-grizzl-optional

Make grizzl optional dependency
add fossil support
Merge pull request #141 from kartoffelbrei-mit-muskatnuss/master

Add fossil support
Mention ido-flx in the README
Clean up and extend the README a bit
Minor change
Fix a typo
Update Changelog
projectile-switch-project now runs projectile-find-file instead of dired
Bump version to 0.9.2
Extend section on keybindings
Fix current version string
Stop using cl completely
cl-flet is not actually a 1:1 substitute for flet
Code style
Adjust some switch project prompt messages
Bump s.el and dash.el deps
Bump the version to 0.9.3-beta
Add command `projectile-find-file-in-directory` (fixes #84)