Merge pull request #41 from mk200789/master

modified experience system
Fixed minor bug with floating point experience gained. Minor code cleanup.
Rewrote battle animation sequence from scratch. Battle animation sequence now registers normal, critical, and magical attacks on a per-unit basis (provided unit has appropriate animations, stats, and weapon). Merged new experience system to new battle animation sequence. Improved new experience system and enemy item drop system to accommodate for all possible attacker/defender scenarios.

** Existing bugs from old battle animation sequence still persists. **
Fixed bug with battle animation sequence where health clamps references incorrect unit.
Fixed major bug when enemy initiates attack and enemy is defeated via a counterattack, the game would do weird stuff (ranging from game freeze to stacking battle animations).
Applied modified critical attack frames to hero_battleanim.js. Cleaned up hero_battleanim.js.
Modified checks for spell screen effects to be based on weapon (tomes) instead of affinity. Minor code cleanup.
Fixed bug with main player (assassin) battle animation sheet not displaying during battle animation sequence. (?)
Fixed bug where units triggering critical hits in battle animation sequence would freeze the sequence (added missing checks for critical hit frames).
Quickfix for dynamic unit animation sheet sizes when swapping attack animations during battle animation sequence.
Fixed computation bugs with unit's accuracy (unit attacks sometimes missing despite GUI displaying 100+ hit).
Fixed reversed display for active unit's and target unit's critical hit rate in battle summary modal.
Added placeholder for magic triangle (currently disabled).
Refactored item usage and weapon durability decrement.
Fixed bug with invalid cleanup and spawning of inventory item interaction buttons. Refactored item usage decrement in inventory item use.
Added/updated helper functions/methods descriptions.