Decode query params keys

[wagjo]

Collection values are encoded into query params with brackets attached as a suffix. When parsing back the url query string, the keys are not decoded. As brackets in query keys tend to be percent encoded in several tools, parser should decode them.

Example of such query, github percent encodes brackets in the href of the following link automatically:
http://example.com/search?terms[]=foo&terms[]=bar

[wagjo]

Fix is provided in #94