Cli enhancements

Few enhancements for gem_dependency_checker and git_gem_updater cli utilities. Now both will parse the ~/.polisher/config file for various config pertaining to build targets (all options overridable via command line). 

When testing git_gem_updater.rb via the savon gem, most of update process works save dependency & file lists which still have some edge cases that need to be addressed. Was working on a little while back, will continue tackling this going forward