Merge pull request #2 from ericmoritz/feature/downloaders

basic implementation of the downloaders
made errors in the download crash the program
Made the Downloaders return an Either in case they fail
Added a function to generate the filename and line number of a failing dep
fixed some var shadowning and used Dep.errorline
used errormsg and fixed the pwd of the git checkout command
fixed the cp command for the local downloader
Removed the invalid top-level dep to make recursion work
Added a test rule for running get-deps in test-data/
fixed the url for the deps git repo
deleted the directory if the clone or checkout fails
a vestage module
Merge remote-tracking branch 'origin/develop' into feature/downloaders

Conflicts:
	src/DepTool.hs
	src/Downloaders.hs
	src/Downloaders/Git.hs
	src/Downloaders/Local.hs