Switch to RubyMotion gem tasks template to get rake gem:release task

Author: andrewhavens

Rakefile

@@ -4,9 +4,8 @@ $:.unshift("~/.rubymotion/rubymotion-templates")
 
 platform = ENV.fetch('platform', 'ios')
 require "motion/project/template/#{platform}"
-
-require 'bundler'
-require 'bundler/gem_tasks'
+require 'bundler/setup'
+require 'motion/project/template/gem/gem_tasks'
 
 if ARGV.join(' ') =~ /spec/
   Bundler.require :default, :spec