Library fails to parse URNs with both R and Q components

[danielthepope]

We've identified an issue where, if a URN contains both an r- and a q- component, the library fails to parse the r-component correctly.

urn:example:foo?+key=value?=fizz=buzz says the r-component is key= (value is empty string). We believe there is an issue with the regular expression that is trying to extract the r-component.

The issue also occurs when the URN contains a f-component, either with or without the q-component.

[danielthepope]

We will be submitting a PR shortly that will fix this issue.