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
Remove UTF-8 -> UTF-16 -> UTF-8 encoding dance to avoid JRuby bug.
Support custom ignore exceptions for background notifications

Closes #95
update CHANGELOG
Turn exception_notification Rails agnostic

Dont believe me?! then, checkout the sinatra example. ;P
Add missing entry to Changelog.
Customizable Mailer class