Put javadoc to gh-pages after each successful build.

Configure Travis to generate and push javadoc to the gh-pages branch
after each successful build. You can view the javadoc at:

http://zk-1931.github.io/javazab/javadoc
Merge pull request #14 from m1ch1/doc

Put javadoc to gh-pages after each successful build
Simple implementation of Zxid
Update access token for travis.
Merge pull request #15 from m1ch1/doc

Update access token for travis.
Add a link to the javadoc page.
Merge pull request #4 from EasonLiao/master

Add a class for zxid