don't even go to the DB for 0 wiught terms
Merge pull request #234 from Connexions/search-returns-books-first

Always return all the books first in search results
ignore all non-quoted stop w words
add non-zero weight for parentauthor test
Install memcache and use it to cache searches

Memcache servers and the cache expiration period can be configured in
the ini file.

Caching can be disabled from the API using nocache=True
Cache subject searches for longer