Add department model and service.
Add department to includes
Add department spec fixtures.
Add department tests.
Fix bug in NameEntity string validation where it would crash when the method calling names_cannot_contain_invalid_characters didn't have every single property.
Add validations to Department model
Add tests for sub-departments.
Add method for checking if a Department is a sub_department?
Add Department model spec.
Update readme to indicate that Department is now implemented.
Adds Class model and service.
Attributes total_tax within the TransactionTaxDetail model and rate_percent
within the SalesItemLineDetail model should not be set by default. Using
the :to_xml with no nil? check automatically creates that attribute within
a request. Using the proc returned from to_xml_big_decimal method does
do a nil check.

Lastly, the percent_based attribute
within the TaxLineDetail model should be a ROXML boolean.
Fix bug in NameEntity string validation where it would crash when the method calling names_cannot_contain_invalid_characters didn't have every single property.
Add class fixtures.
Add Class tests.
Fix error in Class.sub_class? spec.
Minor Class delete method change.
Update readme that Class endpoint is fully implemented.
Merge pull request #88 from minimul/dont-send-if-nil

Attributes total_tax within the TransactionTaxDetail model and rate_percent ....
Merge pull request #87 from markrickert/department

Fully implemented Department