Fixes race condition

In the case that two dependencies are affecting the same package we'll have to
check for a lock in the install dir. If exists just wait for the other child
processes to finish.
Merge pull request #3 from elcuervo/fix_race_condition

Fixes race condition
-H flag adds HEAD to the Godeps file.

Closes #1
Update README.md
Huh, weird, this should have broken the tests locally?
Updated Docs. :)
Update README.md
Update README.md
Update README.md
Update README.md
fail if Godeps file is not present
Merge pull request #8 from icholy/master

fail if Godeps file is not present
Trim down revision number
*Correctly* trim whitespace in HEAD SHA
Adds support or mercurial and bazaar

Closes #6
Merge pull request #9 from pote/support_hg_and_bazaar

Adds support or mercurial and bazaar
Update README.md
Updated docs
Update README.md
Local dependency dir