Added stop and dump features to TestCase

[girardinsamuel]

This PR adds:

1. adds dump() method to a TestCase:
   By default when printing something in a unit test, it's not printed in the console excepted if the test fails. To allow printing data, a dump() method has been added to TestCase (a title can be optionally provided):

self.dump({"test": "key"}, "dump test")

2. adds stop() method to a TestCase: to make a test stop. A message can be provided

self.stop("I wanted it !")

.3 adds helpers to HTTP test responses:

self.get("/").dumpSession().dumpResponseHeaders().assertOk()

• dumpSession: dump session data during a test
• dumpRequestHeaders: dump request headers during a test
• dumpResponseHeaders: dump response headers during a test
• ddSession: dump session data in console during a test and die (test stops)
• ddHeaders: dump request and response headers in console during a test and die (test stops)