Updates the README
Moves the datetime module to a utilities package
Renames the datetime tests to something more appropriate
Extracts the GoesDataSet test suite into a new file
Changes the test file name to match the class it is testing
Extends the GoesFile class to read and manipulate magnetometry data too
Extracts the GoesFile class into a new module
Updates the comments
Extracts the file field name dictionaries into constants on the module
Adds the magnetic file type to the DataSet class
Refactors the filetype name for magnetometric file to magnetic
Moves the DataSet class to a new module