FakeFormatTest: Clean up

Removed left over comments from the top of this test.

Removed unnecessary helper method, replacing it with an
"expectedExceptions" annotation instead.
ImageMetadata: refactor length-1 axis handling

Trailing length-1 axes (e.g. 5,5,2,1 but not 5,5,1,4) are not
significant to calculations and can in fact cause problems in other
software, such as when translating dimensions to ImgLib2.

With this in mind, the ImageMetadata class will now disregard any
trailing length-1 axes.

Closes #119
Remove junit tests

JUnit tests are currently not picked up automatically by maven,
presumably because of the pom changes required to run the testng suite.

For now, the solution is to standardize these tests as testng.