Added guest user session and guest object as current user. Also changed chat to work with this model.
Merge branch 'add_guest_session' into dev
fixed save button bug on new doc page, when a user clicks save now, it will save the new doc
delete the old editor div to fix the issue when a user clicks the new button on doc view, it will show the code editor now
add drop down for mode, set default value of theme in the drop down menu, set default mode for files with extension as .js .rb .java .html .css
Fixed UI related to 'Doc' and 'Folder' views