Single hostgroup view improvements

* Refactored state_history code from status_detail to a snippet
* status hostgroup now has a history tab
Merge branch 'master' of github.com:opinkerfi/adagios
Unit Tests added for troubleshooting purposes.

Run them with: ./manage.py test
changes to sidemenu
font-size for host table now same as services and hostgroups
Objectbrowser -> Forms -> Default value for single choice fields is now a blank value

Fixes #97
More unittests added
More descriptive placeholder for timestamp fields
Experimental Perfdata view added
Merge branch 'master' of github.com:opinkerfi/adagios