Properly align 'Change password' form for smaller screen size.

[rupav]

I'm submitting a ... (check one with "x")

• [ ] bug report
• [x] feature request
• [ ] support request => Please do not submit support requests here, instead ask your query in out Gitter channel at https://gitter.im/fossasia/susi_server

Current behavior:

Expected behavior:

Centrally aligned just like logout button on top.

Steps to reproduce:

Log in, then click on logout to go to logout page. then click on click to change password. start reducing the size of screen.

Would you like to work on the issue? Yes