Fix db name validation. Closes issue 42.
Fix db name validation. Closes issue 42.

hdmessaging/couchbase-mapping-python,erikdejonge/rabshakeh-couchdb-python-progress-attachments,jur9526/couchdb-python,gcarranza/couchdb-python,ssaavedra/couchdb-python,oliora/couchdb-python