Bump minor version to 1.1.0

* [FEATURE] Add `icon` helper
* [FEATURE] Add `font_awesome_css` helper
* [FEATURE] Add `dropdown` helper
* [FEATURE] Add `progress_bar` helper
* [ENHANCEMENT] Add `:fieldset` option to decide whether `fields_for` should wrap fields in a <fieldset> tag
* [FEATURE] Add `button` helper