Fixed methods interpreting the this paramter wrong (the most of them)
Merge pull request #46 from Turakar/turtle-dev

IMPORTANT FIX for Turtle API
Really fixed the turtle methods which interpreted the this parameter wrong
Merge pull request #48 from Turakar/turtle-dev

Really fixed the methods which interpreted the this parameter wrong
Fixed turtle.detectUp and turtle.detectDown
Merge branch 'turtle-dev'