Code cleanup and refactoring

Performed a few minor changes to the code. All functionality should remain normal.

Cross compatibility with 1.7, 1.8 and 1.9

As the title says.

InstantBreak v1.1

This version will not work with anything below Spigot 1.9!

• Spigot 1.9 support.
  • Now uses getItemInMainHand() instead of deprecated getItemInHand().

InstantBreak v1.0.1

• Added blocked-worlds option to config.
• Added an ability to only instant break while holding a certain item.

InstantBreak v1.0.0

• Fixed the listener not listening

InstantBreak v0.0.1-SNAPSHOT

• Added AAC support.
  • It won't flag for FastBreak.