Upgrade error-prone's EqualsHashCode and EqualsIncompatibleType from …

…Warn -> Error (#298)

Fixes #297

Enables [`EqualsHashCode`](http://errorprone.info/bugpattern/EqualsHashCode) and [`EqualsIncompatibleType`](http://errorprone.info/bugpattern/EqualsIncompatibleType) as `ERROR` for Errorprone.

gradle-baseline-java/src/main/groovy/com/palantir/baseline/plugins/BaselineErrorProne.groovy

@@ -19,6 +19,7 @@ package com.palantir.baseline.plugins
 import net.ltgt.gradle.errorprone.ErrorPronePlugin
 import org.gradle.api.GradleException
 import org.gradle.api.Project
+import org.gradle.api.tasks.compile.JavaCompile
 
 class BaselineErrorProne extends AbstractBaselinePlugin {
 
@@ -30,6 +31,14 @@ class BaselineErrorProne extends AbstractBaselinePlugin {
             // TODO(rfink): This is somewhat ugly. Is there a better to add the processor dependency on the library?
             errorprone "com.palantir.baseline:baseline-error-prone:${extractVersionString()}"
         }
+
+        project.tasks.withType(JavaCompile) {
+            options.compilerArgs += [
+                    "-XepDisableWarningsInGeneratedCode",
+                    "-Xep:EqualsHashCode:ERROR",
+                    "-Xep:EqualsIncompatibleType:ERROR",
+            ]
+        }
     }
 
     private String extractVersionString() {