Removing aspectjrt check

[ashj11]

Related to #93.
There are two cases in this.

1. In the case of certain plugins like Firebase, they do operate on the jars and provide the extracted class files are input for the next transformation. In this case, though the aspectjrt class files are present in the path, the above check will fail.
2. In the case of android integration tests, the aspectj runtime doesn't seem to be explicitly passed( not sure why ). But if i bypass the check and still allow it to weave, the weaving seems to be happening just fine. And the test passes.
3. Even if we remove the hasAjRT check, If the aspectjrt is not genuinely present, then weaving fails with a very clear message to check for aspectrt.jar in the classpath, which seems to be good enough.
   @Archinamon given point 3, was there any strong reason for adding the jar presence check? If not, can we remove it.

[Archinamon]

Clear reasons to remove it :)