Extended the Xor.pm Goodie to be able to use the bitwise 'and' and 'or' ...

...operators, as well as parantheses.

This is in reply to Issue #141.

Xor.pm:
- Changed the description and secondary examples to reflect the new functionality.
- Added keywords for 'and' and 'or' as well as the unicode symbols for those operators.
- Changed the split() so it produces a token list with the numbers and the operators.
- The tokens are parsed and a command string with the values and operations is created.
- Perl's eval() is used to execute the command string, and in case of success the result is returned.
- Didn't change/add to the attribution. This is my first try at Perl and I was not sure if there can be two 'github' entries for the attribution section.

Xor.t:
- Added tests for the new operations and for operations with parantheses.
- Added tests for hex and binary values.

System: OSX 10.9
Perl: Active Perl 5.18.1