Allow MML files to be provided #25
Description
Use millistone to be able to take in a .mml file.
I don't think modifying grainstore is worth while, instead make a wrapper including grainstore that encompasses all 3 inputs (grainstore/mml (millstone)/xml)
- Take in local mml file with local datasource
- Take in local mml file with remote datasource
- Take in local mml file with remote zipped datasource
- Take in remote mml file and treat it like a local mml file