secret_keys updated for twitter and google+
manifest file modified and cleared up unnecessary code
browser_action adjusted and is also used to render the log-in function
for twitter and google plus
login_gui file created for google+
The second way for google plus login

This is an alternave way to avoid the chrome extension content security
policy violation. However, the functionality is quite limited when
loaded from the plug-in.
login_gui files added for twitter

login_gui2.js file follows the same design pattern as we used for the
other social website, such as facebook, instagram and so forth.
However, due to the chrome content security limitation, the
login_gui.js file seems to be a better solution to tackle the login
function for twitter in our extension.
An alternative and stable way to handle twitter login and tweet.

Inside of the model.js file,some functionalities were added for twitter
using the same design pattern as the other account types do.
Merge branch 'xinsong' of https://github.com/sheankim/fabula into xinsong

Conflicts:
	src/browser_action/browser_action.html