* FEATURE: introduces minimum trust level for polls
This commit makes `poll_enabled` less misleading and introduces `poll_minimum_trust_level_to_create`. If poll are enabled they will always be cooked, and if you have the required trust level you can create polls. As a side effect, it also fixes a bug where rebaking a post created by staff member when `poll_enabled=false` would end up not cooking it.
It also adds more tests to ensure settings are respected.
* admins should be whitelisted
* checks for admin in post validation
* test for >= instead of == trust level
* Fix infinite loop when poll step is zero
* Add test for step minimum and for breaking test
* Remove trailing spaces (eslint)
* Remove extra space (eslint)
* Removed test call .twice
* renames `select-box-kit` into `select-kit`
* introduces `single-select` and `multi-select` as base components
* introduces {{search-advanced-category-chooser}} as a better component for selecting category in advanced search
* improves events handling in select-kit
* recreates color selection inputs using {{multi-select}} and a custom {{selected-color}} component
* replaces category-selector by a component using select-kit and based on multi-select
* improves positioning of wrapper
* removes the need for offscreen, and instead use `select-kit-header` as a base focus point for all select-kit based components
* introduces a formal plugin api for select-kit based components
* introduces a formal pattern for loading and updating select-kit based components:
```
computeValue()
computeContent()
mutateValue()
```
* Add rubocop linting to docker:test rake task
* Add eslint JS listing to plugin files, and add SKIP_LINT variable
* Fix failing ‘polls’ plugin eslint
Using eslint-disable-line, as is done in core qunit tests such as `acceptance/group-logs-test.js.es6`
* Add plugin test eslint to travis config
* Merge some eslint lines
