Updates to messenger

1) Namespacing all internal classNames with "messenger-"
2) Applying messenger-on-right and messenger-on-left styling only when used in conduction with to messenger-on-top or messenger-on-bottom
3) Namespacing .fixed-messenger to ul.messenger
4) Adding cursor pointer to all messenger actions links
5) Use a media query to style the messenger-on-top and messenger-on-bottom versions for browsers under 960px in width
6) Add the class messenger-empty to ul.messenger when it contains no shown messages
7) Only add the messenger-actions container when there are actions for a message
8) Add the class messenger-message-inner to the div containing the actual message text
9) Use class names to show/hide messages instead of inline styles
Adding two messenger theme: Block and Future
Cross-browser `user-select: none`
Assume no bootstrap dependency for close styling in future theme
Merge branch 'master' into gh-pages