Added functionality for swipe to move to topics and back

[zeerorg]

Implemented navigation idea #442
Short clip demonstrating use: https://drive.google.com/open?id=0BxknwnHbF5oERllfUlF4X0VPUWc

[smarx]

Automated message from Dropbox CLA bot

@zeerorg, thanks for the pull request! It looks like you haven't yet signed the Dropbox CLA. Please sign it here.

[saketkumar]

@zeerorg Nice work. but this shouldn't happen. Disable the right swipe on home screen.

[Sam1301]

@zeerorg this looks great! 👍
Can you please address Saket's comment here?

[kunall17]

• You should change the git commit author details to match your github account!

[kunall17]

@zeerorg this is a nice feature to be implemented, can you fix the comment which saket has posted?

[zulipbot]

@zeerorg, your pull request has developed a merge conflict! Please review the most recent commit (f791888) for conflicting changes and resolve your pull request's merge conflicts.

[zulipbot]

@zeerorg, your pull request has developed a merge conflict! Please review the most recent commit (470ade3) for conflicting changes and resolve your pull request's merge conflicts.

[saketkumar]

@kunall17 What about this PR? I really loved the feature.