Minor fixes

[TheBB]

First commit: saving as g2 won't work if controlpoints is a matrix, it has to be an array (this has to do with how iterating over an array works vs. iterating over a matrix). This might be worth fixing in g2 output instead of here, though.

Second commit: For consistency.

[VikingScientist]

We might want to consider specifying the return-self behavior in the documentation. Has to be done for all of the functions which does this

[VikingScientist]

Add the "return self" behavior to the documentation and then we'll pull this in.

[TheBB]

Done :+1: