Ensure blog is installed before creating tables.

[peterwilsoncc]

WP fires the plugins_loaded hook during the install process, causing the Cavalcade tables to be created before the options table exists.

Without an options table, Cavalcade is unable to store the version of the database it is using it ends up considering all sites to be using version 1 of the database schema.

This adds a check to ensure is_blog_installed() == true before adding the Cavalcade database tables. I'm not sure how this affects multisite so would value any feedback.

Fixes #73

[joehoyle]

Hmm @roborourke @rmccue did we just fix something similar to this? Seem to remember needing to patch cavalcade when WP_INSTALLING was set... something along those lines?

[roborourke]

The issue is more to do with the runner, it doesn’t really handle a pre installation state and generates errors or quits the service entirely

[joehoyle]

Ok thanks @roborourke, @rmccue can you review and merge accordingly?

[rmccue]

@peterwilsoncc can you update per above? (I can't commit to your fork :) )

[peterwilsoncc]

Requested changes committed along with updates from master.

[peterwilsoncc]

@roborourke @rmccue Bumped with master again to include the CI fix. Tests are now passing.

It'll need some confirmation that the changes to plugin.php and namespace.php don't screw anything but testing locally it looks good to me.

[stuartshields]

@roborourke Can you approve and merge this PR in for @peterwilsoncc

[roborourke]

@stuartshields yeah, been meaning to test it locally. I was hoping to get #91 in first because the bulk of the tests are actually skipped right now