Embedded the numpy upcasting inside the Quantity class.
Cleanup of commented code.
Implemented the .add() method with numpy awareness and added a test.
Removed comment.
Removed unused code.
Implemented __sub__ support.
Added tests for addition and subtraction.
eol fix.
Formatting, mostly for line length.
Remove wasted lines.
Formatting and added plurals.
Fixed spacing.
Added tests for bumpy slicing.
Added exception type..
Correctly match all types.
Added inline function to copy the units[] array.
Formatting and commenting.
Commenting and formatting.
copy() function for the numpy version.
Removed deleted lines.