Adds a constructor to url taking a string.

f# doesn't do implicit conversions.
Changes for @thecodejunkie
Merge pull request #1441 from Curit/url-constructor

Adds a constructor to url taking a string.
Ripped the conneg parts out of DefaultRouteInvoker
Made response negotiator configurable, tests passing
Some refactoring of DefaultResponseNegotiator
Added some tests for DefaultRouteInvoker
Moved check for existing response into negotiator
Fixed error after rebase
Updated build status badges..

..to point to the new TeamCity CI box.
Fixed date time test for DST
Merge pull request #1348 from khellang/response-negotiator

Response Negotiator