Adds support for search

Also refactors Headquarters::Request a bit
I thought I had commented on this already

I did because we're most likely going to use mainly the `params` hash in our main methods. The rest of the options, as far as I can see from the [httparty list of options](http://www.rubydoc.info/github/jnunemaker/httparty/HTTParty/ClassMethods),  are only for configuration and other lower-level stuff, which if used, will be in global configurations, and not per request

So we would be force to always do

    Request.new ..., query: { q: 'is:open' }

instead of just

    Request.new ..., q: is.open