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
Added priority support to events
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