minor change
A file skills/SkillMapper.java is updated - its efficiency and security are improved.
Module 'controllers' and 'skills' are modified to provide more flexible mapping between keys and skills. For the module 'controllers', a new class - 'Key' is added. For the module 'skills', a new file 'SMapDrive' is added. The SMapDrive is new driver class to map skills with keys and it will replace 'SkillMapper' class soon. The 'Skill' class is modified to interect with the 'SmapDrive' class. Test module is also updated to test it, and a test file - 'TestSMapDriver.java' is added.
Merge pull request #21 from TheDizzler/Wonho

Wonho