[Backend] Added the mailers classes
[Backend] Rebased
[Front-end] [#181] Cancel button added
[Front-end] [#181] Refreshes state when joining, leaving and posting
[Front-end] [#181] Refactored activity field watcher to watch the specific fields, added flash when edit is successful, fixed bug in activity put interceptor where it wasn't converting endingtime into a moment obj
[Front-end] [#181] Added a gray coloring for edit pencil button, added edit button for description
[Front-end] [#181] Added utility class to check time range validity, added validation logic for editing time
[Front-end] [#181] Increased visibility of available date range
[Front-end] [#181] Improved UI when editing activity fields
[Backend] Finished comments update and updated the docs for comments update.
Merge branch 'master' of https://github.com/omfgitsjack/justplay into frontend
[Front-end] [#181] Implemented the put in comments.
[Front-end] [#177] Began refactoring code for two panes