Fixing typo and missing expected text in test.

The test file is "phototest.tif", and now that this is fixed, the
expected text must be provided to make the assertion pass.
Allow alternate test image in BaseApiTester.

If an argument is specified, it will now be used as the path to the test
image.
Merge pull request #8 from tausten/master

Initial minor updates to fix a bug in unit test code, and allow specification of non-default test image in BaseApiTester.