fix error  when running "gradle eclipse" with gradle 2.0 :

Execution failed for task ':eclipseClasspath'.
> java.io.File cannot be cast to org.gradle.api.artifacts.Configuration

fix from http://forums.gradle.org/gradle/topics/eclipse_plugin_broken_with_2_0_rc_1
Merge pull request #3 from davidB/master

fix error  when running "gradle eclipse" with gradle 2.0 :