updated version of activemodel 3.2.8 -> 4.1.1 to fix issues with rails

Rails uses newer version of active model

------ Error message:
Bundler could not find compatible versions for gem "activemodel":
  In Gemfile:
    mvg-live (>= 0) ruby depends on
      activemodel (~> 3.2.3) ruby

    rails (= 4.1.1) ruby depends on
      activemodel (4.1.1)