Enable ErrorProne in the pom.xml

Use version 2.0.5 of ErrorProne. From version 2.0.6 JDK 8 is
required [1].

[1] https://github.com/google/error-prone/issues/369

Change-Id: Ib4fa6514d09ea6c3ea758ce08383627eca24da57

pom.xml

diff --git a/pom.xml b/pom.xml
index f9a44f6..4a2c8d6 100644
--- a/pom.xml
+++ b/pom.xml
@@ -374,10 +374,26 @@
         <artifactId>maven-compiler-plugin</artifactId>
         <version>3.5.1</version>
         <configuration>
+          <compilerId>javac-with-errorprone</compilerId>
+          <forceJavacCompilerUse>true</forceJavacCompilerUse>
           <source>1.7</source>
           <target>1.7</target>
           <encoding>UTF-8</encoding>
         </configuration>
+        <dependencies>
+          <dependency>
+            <groupId>org.codehaus.plexus</groupId>
+            <artifactId>plexus-compiler-javac-errorprone</artifactId>
+            <version>2.7</version>
+          </dependency>
+          <!-- override plexus-compiler-javac-errorprone's dependency on
+               Error Prone with the latest version -->
+          <dependency>
+            <groupId>com.google.errorprone</groupId>
+            <artifactId>error_prone_core</artifactId>
+            <version>2.0.5</version>
+          </dependency>
+        </dependencies>
       </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>