Solr4 bugfixes

Discovered that commit wasn't being called on the solr4 index, causing newly uploaded documents not to appear.  After discussing our current document upload/update rate w/Ted, we decided to call commit manually and dial back the autoCommit to every 10 minutes.

Also upgraded sunspot_solr gem in order to get a bugfix for the sunspot:solr:stop rake task
failing on Ubuntu w/kernel 3.x.  The bug is discussed further in the sunspot pull request:
 https://github.com/sunspot/sunspot/pull/221