Minor changes

-removed minus from integer
-handled exceptions, now prints to error stream as required

LEFT:
-wait for forum answer regarding int limits
(as for now it will throw an error on -2^31, although a valid integer)
-check what is the correct format of the table output, it looks kinda
buggy, maybe compare with other people
-test strings and comments
-run the tests that are in the skeleton file in moodle