Refactor Makefile

Use dependencies.

Signed-off-by: Stephen Celis <stephen@stephencelis.com>

Conflicts:
	Makefile

Signed-off-by: David Celis <me@davidcel.is>
Add ag.vim

Signed-off-by: Stephen Celis <stephen@stephencelis.com>

Conflicts:
	.gitmodules

Signed-off-by: David Celis <me@davidcel.is>
Add rbenv back to Makefile

Signed-off-by: Stephen Celis <stephen@stephencelis.com>

Conflicts:
	Makefile
	janus/gitgutter

Signed-off-by: David Celis <me@davidcel.is>
Update submodules

Signed-off-by: David Celis <me@davidcel.is>