Merge pull request #2 from jtjeferreira/patch-1

Update mainClass

Author: Fadelis

protoc-gen-java-optional/pom.xml

@@ -46,7 +46,7 @@
           <archive>
             <manifest>
               <addClasspath>true</addClasspath>
-              <mainClass>org.grpcmock.protoc.OptionalGenerator</mainClass>
+              <mainClass>org.grpcmock.protoc.plugin.OptionalGenerator</mainClass>
             </manifest>
           </archive>
         </configuration>