Adding SetEnv proxy-nokeepalive and proxy-initial-not-pooled to help cut down on the Proxy Errors in apache.

See:
- http://httpd.apache.org/docs/2.2/mod/mod_proxy_http.html
Using the java cookbook to install & manage java, rather than the jenkins::java recipe.

Locking jenkins cookbook to ~> 2.0.0

Version bump to 0.2.6