Add requires to fix resolution of the wrong Sunspot constant

@hollocherdale and I tracked this down at the 7/26 code sprint:

The references to :Sunspot were finding the global one defined in
the Sunspot gem; because that constant already existed, Rails'
magic constant loading didn't get invoked to find ours.

Fix by requiring ours explicitly. (Requiring sql too, just for
symmetry and future protection against a global Sql constant.)
Fix solr startup: wait for it on the port it's running on.

(i.e., if you happen to tell it to start with RAILS_ENV=production,
we'll look for it on the production port...)
Default all tests to use Sql; turn Sunspot on conditionally
Fix tests' Sunspot/Solr running check

Instead of seeing if any Sunspot/SLR server is running, see if
one is listening on the port we'll communicate on.
Merge pull request #163 from bryanstearns/search_fixes

Search fixes