Merge pull request #3 from blackvladimir/master

check if obj is an object, and raise meaningful exception
Update
Update
Update
Adjusting VIEW command
Bugfix
Update - Czech commands
Update
Update
Update
Update
Update
Adding test to CUBE
Adding many tests.
Started multilingual error messages
Small improvement
Bugfix
Bugfix
Changing the ROTATE command
Adjusting SCALE command