revert versions to the way they were since it broke publishing, added unit test to ensure they're in sync

resolves #117. The XML-formatted strings in a few raw_metadata are now parsed into OrderedDicts. This isn't exposed to the user but if we want to add any of the data it will be more convenient for contributors to examine the contents of the data

resolves #103: ND2s with a single image could not be parsed properly as they do not contain any dimension data, so when absent we can assume a single frame exists