Spaces encoded as plus in URL aren't converted prior to query

If a search URL has spaces encoded as plus signs (+), they aren't decoded before the query is sent to Google. Also, they will be added in the form on the results page. For example: search/google?query=web+developer will be searched as the literal "web+developer", which will also be the pre-filled value of the keywords input on the page.

This patch will replace + with %20 prior to calling decodeURIComponent().

This solution is based on the answer here: https://stackoverflow.com/a/24417399