PY3: Add __eq__ method to GeneticCode

Python 3 dropped support for the __cmp__ method, meaning that when you compare
two objects it will not care about the result of  __cmp__, however if you add
the __eq__ method, all works perfectly.

                                  --------------
               ._ o o            / Python 3 is  |
               \_`-)|_          /  for sinners  |
            ,""       \        /----------------
          ,"  ## |   ಠ ಠ.     /
        ," ##   ,-\__    `.
      ,"       /     `--._;)
    ,"     ## /
  ,"   ##    /

Geraffe credit to:
http://www.reddit.com/r/pics/comments/8aqjh/awww_this_is_just_too_sad_pic/c08pp5z