Add commit field for bypassing verification (--no-verify)

This new field toggles whether or not we will pass --no-verify to `git
commit'.

Default keybinding: C-c C-n
the magit-blame-mode test seems to cause issues in travis
Merge branch 'maint'

Conflicts:
	tests/magit-tests.el
Merge commit '831ca7e92435033a30f7c00ab9b3240ecb7c96b2' into mgalgs/no-verify
Merge branch 'mgalgs/no-verify'
compute default pattern the same M-x grep does