adding a test matcher allowing to test for absence of a parameter
aligning Event's event builder to the style used by other parts of the library
Merge branch 'master' of https://github.com/tasubo/jgmp
improving AsyncHttpRequester test's resiliance against timing issues.

It will now finish as soon as all requests have been executed, but at most 1 second.
Merge pull request #7 from mkischel/bugfix/async-requester-test-timings

Bugfix/async requester test timings