Add % to valid url query string characters

[RobvH]

This addresses issue #74

Query strings can include all url encoded characters, often beginning with '%'.

Without this patch, this common and valid url fails validation: https://example.com/app?value=two%20words

Hope this helps!

[coveralls]

Coverage remained the same at 89.32% when pulling 41542b1 on RobvH:RobvH-validate-percent-encoded-urls into 01bf6ba on thedevsaddam:master.

[thedevsaddam]

Can you please set the target branch to dev?