Fixed bug with spaces in stub requests

The webmock gem was [updated to version 1.11 yesterday](https://rubygems.org/gems/webmock), which was causing the most recent build on Travis CI to break. I ran bundle update on my local machine and recreated the error. A small change to the client spec -- removing URL-encoded spaces from the stub request for #author_by_name -- got the tests to pass again. You may want to require webmock 1.11 in the gemspec, since the current tests will fail in earlier versions.