Stack names should be independent of the github URL of the repository

[mburns]

We hardcode the way we construct github URls from a stack. Currently, we have ele.js, noit.js and chef.js stacks which map nicely to github.com/racker/{ELE,CHEF,NOIT}.git

We want to be able to have a test.js stack or dev.js stack that relies on a github repository that has nothing to do with test.git or dev.git.

• https://github.com/racker/dreadnot/blob/master/lib/stack.js#L157-L160
• https://github.com/racker/dreadnot/blob/master/lib/stack.js#L163-L166

Dreadnot should add an option to specify the repository in the stack config and prefer that over github.com/racker/FOO.git