Fixed a spacing bug with the output of GetMatrix().
Added unit tests to verify spacing is correct for various sentences that use GetMatrix() where existing tests couldn't be used.
Added a unit test to verify that an XML output file will be handled if specified (no output yet).
Added method to actually do the XML serialisation.
Added some checks around valid filename and path details.
Added unit tests to cover various situations.
Added a couple of other unit tests.
Merge pull request #13 from TimCollins/add-xml-serialisation

Add xml serialisation