Added git push options to avoid logging github keys

Just got a notification from github that my build was logging out via Travis my personal token and I thought I'd to the right thing and help anyone else that may follow your blog.  Here's a snippet fromt he logs (I have since revoked this token):

```sh
...
[gh-pages 95fc552] Travis build 321
 6 files changed, 104 insertions(+), 104 deletions(-)

Total 12 (delta 7), reused 0 (delta 0)
To https://51feae247e219008bff16d68adc8a667f1abf85e@github.com/johncarl81/transfuse.git
   378d2fa..95fc552  gh-pages -> gh-pages
travis_time:end:1ace1961:start=1411675846847497871,finish=1411675850359791272,duration=3512293401

The command "./build.sh" exited with 0.
```
https://travis-ci.org/johncarl81/transfuse/builds/36293333

By the way, did you mean to git push to gh-pages (instead of master) in your example?