Set master to v4.0.0
Remove older versions from readme.
remove jruby support from Travis

Because C extensions are not supported in Travis, while
exception_notification tests relies on sqlite gem, which requires
C extensions. :disappointed_relieved:

Read more:
  * http://about.travis-ci.org/docs/user/languages/ruby/#JRuby%3A-C-extensions-support-is-disabled
Merge branch 'oficial'