Implemented CaptureNodeWithLiteral

After upgrading from 0.16 to 0.17 some of my routes didn't match anymore. And serveral of them coudn't easily be fixed, so I added a TrieNode which combines the LiteralNode with the CaptureNode.

This node can match routes like /image/{id}.png and /google{verification}.html

You could make this kind of matches with the RegexNode but this is way more readable and easier. And it makes Nancy better backwards compatible with 0.16.