Added the support for registration

This PR resolves issue #60.

Following are the features -

[x] First time user clicks on login button.
[x] The user is asked to login through github.
[x] If the user is registered, we check the student.csv for the registered students.
[x] Then the gh_login_student.json is updated, with the credentials of the user.
[x] The user is redirected to dashboard. Few reasons for using two separate files student.csv and gh_login_student.json -
The student.csv contains the list of registered user
The gh_login_student.json contains the data for the current login. This file can be used for displaying the stats of the user. This gets updated every time the user logs in, so no need to fetch data for displaying the data for dashboard. Just plug and use the value.

[x] I haven't added the list of the universities as a drop-down list. Maybe @xypnox can add them.