introduce new module camunda-commons-testing (see issue #4)

this module contains junit/hamcrest/mockito and assertj in the current versions and fixes (junit excludes hamcrest 1.2 and uses 1.3).
The amount of test-scoped imports can be reduced to this single commons module.

Currently provided:

* junit 4.11 (withoud hamcrest-core 1.2)
* hamcrest-library 1.3
* mockito-core 1.9.5
* assertj-core 1.7.0

In addition, this module also provides small extensions and improvements around junit and mockito, such as the ChainedRule and the FluentAnswer. These classes were copied from camunda-bpm-needle and camunda-bpm-mockito where they are already used, making them commonly available.

further changes with this commit:

* eat your own dog food: utils and logging now use testing as sole import for unit testing
* README & links