Fixed an absolute reference to SpongeAPI.

This enables building Sponge as a subproject of another Gradle build. I'm assuming this was an oversight since the other references from the same file were relative.
Add ASMHelper file
Implement forwarding methods for PreInit event

getSuggestedConfigurationDirectory() is still unimplemented
Merge pull request #43 from Raphfrk/event_conversion

Added priority support to events
Merge pull request #42 from Kobata/preinit-forwarding

Implement forwarding methods on PreInitializationEvent
Update README.md
Merge pull request #38 from teozkr/hotfix/sponge-as-subproject

Enable building Sponge as a subproject of something else
Merge pull request #45 from jacklin213/patch-1

Update README.md
Added method from ASMUtils to AMSHelper
Merge pull request #44 from Raphfrk/asm_helper

More asm helper methods
Forge Event Handling change
  Removes directly accessing the forge ListenerLists
  Registers one EventListenerHolder for each event type/priority with forge
  EventListenerHolders are generated dynamically using ASM
  The event listener holder calls all the sponge listeners
  Priorities are grouped since Sponge has more priorities than forge