Do not run Bundler.setup from main library.

Imagine a typical use case for grb:

* User moves to a project dir (~/myproj)
* User uses grb (grb create funtimes)
* grb executes Bundler.setup, which munges Ruby's load path to match myproj's Gemfile.lock
* grb tries to require "rainbow," which isn't in myproj's Gemfile.lock
* grb dies

Gem dependencies are better handled by Rubygems during install, and later by Bundler when running against an
actual app's Gemfile.

lib/git_remote_branch.rb

@@ -1,13 +1,4 @@
 require 'rubygems'
-
-begin
-  require 'bundler/setup'
-rescue Bundler::GemNotFound => e
-  STDERR.puts e.message
-  STDERR.puts "Try running `bundle install`."
-  exit!
-end
-
 require 'rainbow'
 
 begin