Refactor the name of the test helper function.
Refactor the name of the test helper function.

The SenTest Framework runs all methods that return void, take no
parameters and whose name starts with `test`.

The helper function passes 2/3 of these and I think that it is not
immediately clear that it is a helper function. Not part of the
Objective-C coding style.

This commit renames:
- testPath:relativeToDirectory:expectedResult:

to:
- checkPath:relativeToDirectory:againstExpectedResult:

paulkite/KSFileUtilities,mz2/KSFileUtilities,karelia/KSFileUtilities