Fix Travis CI link in the readme
Fix Travis CI link in the readme

Summary:
According to https://travis-ci.org/github/facebook/fbthrift:

> Please be aware travis-ci.org will be shutting down in several weeks, with all accounts migrating to travis-ci.com. Please stay tuned here for more information.

Update the URLs to point to the new location and move the badge to a separate line because it's not aligned with the title properly.

Reviewed By: yfeldblum

Differential Revision: D27924726

fbshipit-source-id: 2fceec7fecb5921fb209dc73b854806df9259a04

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift