Merge pull request #2 from saketkc/master

Improve error rendering, check for receipt file existence
Bugfix for non-versioned dependencies.
Another bug related to picking wrong version.
Enable verbose output the dirty way
Create symbolic links to vbrew script that allows it to operate as brew external commands.

brew vinstall homebrew/science/tophat 2.0.11
brew vdeps tophat 2.0.11
brew vuinstall homebrew/science/tophat 2.0.11
Small refactor, better name for helper.
Support dependencies with revisions.

Closes #9.
Resolve latest revision when using brew-vdeps.

Closes #11.
PEP-8 fix.
Refactor version resolving stuff to be more amenable to use as library.

(Read as 'hack it up for reuse within Galaxy'.)
Add --relaxed argument allowing resolution of env for non-vinstalled recipes.

Will be isolated to the package itself and not its dependencies. For instance:

% brew env --relaxed boost 1.55.0
LD_LIBRARY_PATH=/home/john/.linuxbrew/Cellar/boost/1.55.0_2/lib:$LD_LIBRARY_PATH
export LD_LIBRARY_PATH
More refactoring for consistency and reuse as a library downstream.