Release v2.2.0

Bugfixes:

• Fixed an exception raised when form_group block returns nil (#111)
• Fixed an exception on human_attribute_name when using bootstrap_form_tag (#115)
• Set offset in form_group without label in horizontal layout (#94, @datWav)
• Fixes an offset bug in form_group without a given label in horizontal layout (#130, @datWav)
• Fixed bug where collection_check_boxes doesn't work if all are unchecked (#116, @burnt43)

Features:

• Added the ability to append/prepend buttons (@retoo)
• Added support for time_zone_select
• Accept multiple values, and objects as well, on collection_check_boxes
  checked option (#114)
• Added support for hidding attribute name in errors_on helper (@datWav)
• Added support for additional class to the wrapper form_group by a field (@datWav)
• Support showing error summaries when inline_errors is enabled (@rosswilson)
• Name is now optional when creating static controls
• Keep original form helper methods with _without_bootstrap suffix (#123, @a2ikm)
• Added glyphicon support
• Added i18n support for help messages (#122, @huynhquancam)
• Added the ability to pass any attributes to wrapper (#136, @atipugin)
• Split monolithic test file into several smaller files (#141, @spacewander)
• Added role="form" attribute to forms (#142, @spacewander)