Release Administrate version 0.1.1

- Update gem version
- Update README with recommended optimistic versioning for bundler
- Update README with warning about Administrate's pre-1.0 status
- Update CHANGELOG to fill in missing PR references
- add `[I18n]` category to CHANGELOG
- sort CHANGELOG entries according to change type

Changes:

* [#191] [CHANGE] Improve API for specifying how resources are displayed
  across the dashboard.
  * Models are now displayed with a sensible default - (e.g. "User #2")
  * Users can define `ModelDashboard#display_resource(resource)` for custom
    display behavior
  * Users who have generated views for the following field types
    may need to update them to take advantage of the new API:
    * HasOne
    * HasMany
    * Polymorphic
    * BelongsTo
* [#223] [FEATURE] Translation: Vietnamese
* [#161] [FEATURE] Translation: Mandarin Chinese
* [#196] [FEATURE] Translation: Taiwanese Mandarin
* [#142] [FEATURE] Translation: Brazilian Portuguese
* [#171] [FEATURE] Translation: Polish
* [#153] [FEATURE] Translation: Russian
* [#148] [FEATURE] Translation: French
* [#147] [FEATURE] Translation: German
* [#154] [FEATURE] Translation: Spanish
* [#126] [UI] Preserve whitespace when rendering text fields
* [#194] [BUGFIX] Don't clear out datetime values in form fields
* [#193] [BUGFIX] Don't assume that unrecognized db column types are searchable
* [#124] [BUGFIX] Better detection of application models
* [#156] [COMPAT] Include missing `sass-rails` dependency in gemspec
* [#174] [COMPAT] Make several missing dependencies explicit.
* [#144] [COMPAT] Update repository structure so Bundler can pull the gem from github.
  (e.g. `gem "administrate", github: "thoughtbot/administrate"`)
* [#166] [COMPAT] Use ANSI SQL standards for case-insensitive search
* [#120] [DOC] Add Rubygems version badge to README
* [#165] [DOC] Add CircleCI badge to README
* [#119] [DOC] Add CodeClimate badge to README