Patch for Issue #234 to handle duplicate dependencies

In some instances brew installs packages that have dependencies already
listed as a 'resolved' dependency.  This patch checks the brew info for
each package and builds a list of dependencies-of-dependencies.  If any
of these dependencies-of-dependencies is already slated for
installation, it is removed from the list of resolved packages.
 
Potential Improvements: Currently only one level of dependencies is traversed.  It is possible to build a complete dependency tree, but performance would have to be taken into consideration.