upgrade GMavenPlus dependencies

upgrade GMavenPlus dependencies
1. dependency part about Groovy and Spock
2. plugin part about gmavenplus and source plugin (compiler plugin not included)

dependency part

<dependency>
    <groupId>org.codehaus.groovy</groupId>
    <artifactId>groovy-all</artifactId>
    <version>2.4.4</version>
</dependency>
<dependency>
    <groupId>org.spockframework</groupId>
    <artifactId>spock-core</artifactId>
    <version>1.0-groovy-2.4</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.spockframework</groupId>
    <artifactId>spock-spring</artifactId>
    <version>1.0-groovy-2.4</version>
    <scope>test</scope>
</dependency>

plguin part

<!--FIXME: GMaven plugin is no longer supported, GMavenPlus is the alternative-->
<!--latest GMaven is gmaven-runtime-2.0 only support for Groovy 2.0.x.-->
<plugin>
    <groupId>org.codehaus.gmavenplus</groupId>
    <artifactId>gmavenplus-plugin</artifactId>
    <version>1.5</version>
    <executions>
        <execution>
            <goals>
                <!--<goal>addSources</goal>-->
                <!--<goal>addTestSources</goal>-->
                <!--<goal>generateStubs</goal>-->
                <goal>compile</goal>
                <!--<goal>testGenerateStubs</goal>-->
                <goal>testCompile</goal>
                <!--<goal>removeStubs</goal>-->
                <!--<goal>removeTestStubs</goal>-->
            </goals>
        </execution>
    </executions>
</plugin>
<plugin>
    <!-- if including source jars, use the no-fork goals
         otherwise both the Groovy sources and Java stub sources
         will get included in your jar -->
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-source-plugin</artifactId>
    <!-- source plugin \> = 2.1 is required to use the no-fork goals -->
    <version>2.4</version>
    <executions>
        <execution>
            <id>attach-sources</id>
            <goals>
                <goal>jar-no-fork</goal>
                <goal>test-jar-no-fork</goal>
            </goals>
        </execution>
    </executions>
</plugin>