Add intermediate ReaderTest class to initialize reader and default sizes

#2 broke more tests than it fixed them (see http://ci.openmicroscopy.org/view/Failing/job/BIOFORMATS-5.1-merge-matlab/289/). This PR should now properly fix the MATLAB tests by 
1- creating an intermediate ReaderTest class 
2- adding a `setUp` method which sets the Java class path, initializes a FakeReader and stores the default sizes using the public attributes.
3- moving the reader closing to the `tearDown` method of this new class