SearchRequestMarshaller used by AmazonCloudSearchDomainClient breaks when using structured queries with equal signs in them

This issue is reproducible in 1.8.4.

If you have a structured query string with any '=' in it the URL builder breaks, since it does String.split on equals signs and checks that there are only 2 values in the returned array (line 74 of SearchRequestMarshaller).

According to the documentation at http://docs.aws.amazon.com/cloudsearch/latest/developerguide/searching-compound-queries.html the following query is valid:

q=(and (range field=year [2013,}) (or (term field=title boost=2 'star') (term field=plot 'star'))

But due to this bug the 'q' parameter does not get added to the final string. This pull request fixes this issue.