Add addm Command

[rprouse]

addm

Adds "FIRST THING I NEED TO DO" to your todo.txt on its own line and
adds "SECOND THING I NEED TO DO" to you todo.txt on its own line.

Project and context notation optional.

todo addm "FIRST THING I NEED TO DO +project1 @context" "SECOND THING I NEED TO DO +project2 @context"