Enable checkstyle gradle plugin.

build.gradle

@@ -20,6 +20,7 @@ buildscript {
 
 apply plugin: 'forge' // adds the forge dependency
 apply plugin: 'maven' // for uploading to a maven repo
+apply plugin: 'checkstyle'
 
 version = "6.0.8"
 group= "com.mod-buildcraft"
@@ -114,6 +115,10 @@ jar {
 	from sourceSets.api.output
 }
 
+tasks.withType(Checkstyle).all {
+	configFile = file('guidelines/buildcraft.checkstyle')
+}
+
 // make sure all of these happen when we run build
 build.dependsOn sourceJar, javadocJar, deobfJar, apiJar