System support for RedHat

This commit is adding init.d script and sysconfig file which allows to
run GitBucket in the standalone mode. It also adds the spec file which
allows to build RPM package.
Describe version of Servlet container
Merge pull request #161 from jtyr/master

System support for RedHat
(refs #163)Allow '.' in user name.
Update README.md
(refs #163)Fixed
Merge branch 'master' into SingleSignOn