fix in 'select_available_locales_fields' method

Fixes #251
Remove Versionfile

Users should look for a branch matching the current Spree version
they-re running
Cleaner readme.

lso point to correct localeapp project.
Make master branch less restrict on spree versions

No need to force to 2.1.0.beta as master branch should work as well
spree 2.0.x releases
i18n Sync from Localeapp
Move translation instructions ot the top of README
Auto run migrations when installing the extension
Fixed wrong naming of :en (International) locale.
Added rspec to test group to see if tests will run thru on Travis.
Add missing tooltip titles for buttons.

Fixes #266