Added /add route for adding numbers

Added an /add route that takes a one and two parameter.  These
numbers will be added and reported. Values are checked for
numeric value before use and an HTTP 500 and error message are
returned for non-numeric parameters.
Adding default route test

Checks for HTTP status 200 and known return text.
Adding UA (user agent) route test

Tests for HTTP 200 indicating no error was found while getting
user-agent header.
Adding hello route test

Checks for HTTP 200 and "Hello $name" message text.