Gemfile, tagged specs, exceptions for failed request.. oh my!

Group spec now creates "org" visible group. It is no longer a priviledged spec
Online raises error message from API response.
Added specs for Arcgis::Base api method/url generation.
Added rspec tag to exclude tests that require publisher priviledges.
Added bundler to manage development dependencies.

Also, apparently I don't know how to spell 'privilege'.