Adds 13 new operators.

* Adds bitwise left shift (<<), right shift (>>), OR (|), AND (&), and XOR (^) as well as their corresponding assignment operators (<<=, >>=, &=, |=, ^=) and bitwise NOT (~, one's compliment).
* Adds an exponent operator (\*\*) and corresponding assignment operator (\*\*=).
* Modified an existing test and inserted new tests to ensure the new operators function as intended and respect order of operations.