Optimised add() and remove() methods.
Made SortedArraySet extend ArraySet.
Minor optimisations.
Added a chained HashMap implementation.
Deleted LinkedMap, for it is too inefficient.
Added contains() method to Map.
Moved MultiSet and ArrayMultiSet to the set package. Added capacity checks.
Deleted CapacityExceededException and its package.
Added indexOf() method/
Merge pull request #40 from mfrancis95/mike

Optimisations, HashMap, package changes, and indexOf()