Merge 185-editor-refact (#588)

* slate editor poc #185

* css consolidation #185

* editor serializer and integration progress #185

* switch ReplyEditor to use slate #185

* image drag-drop #185

* image progress, soft returns, serializer compat #185

* link button, block formatting menu, soft returns #185

* add paste html functionality, test images as inline #185

* revert class removal for cleaner diff and merge #185

* insert image as inline, add shortcuts #185

* fix form clear

* add icons and set 644

* add sidebar for inserting blocks, propagate state change to parent #185

* change images back to block elements, use slate fork

* Slate image upload integration (work in progress) #185

* proper node att rendering, use steemit fork, insert block at eof #185

* Implements image upload retry from draft.  #185

* add img.alt attrib to de/serialize

* Catch and report image upload network errors #185

* Configurable image upload server url. #185

* images as inline elements, ul/ol fix

* initial video embed

* vimeo detection

* Add missing data url check, was trying to upload non data urls

* add support for table elements, iframe de/serialize, whitespace normalization workaround

* slate cleanup

* add img proxy and fix attributes rendering

* add support for alignment, clean up serialize rules, use new alt fork

* fix for dupe decs in last commit. whitelist align classes in SanitizeConfig

* new slate build, fix data img render, cleaner raw html

* merge cleanup

* consolidate markdown styles

* remove demo text, add min height

* fix trim bug

* add app/format to meta

* update defaults

* consolidate video embed styles

* fix title input on firefox

* add iframe wrapping, cleanup, documentation

* Fixed tag name regex, minor adjustments in tag name conditions.

* switch back to rte-editor. revert this commit to upgrade to slate.