Set slf4j-api to test, adds enforcer plugin (#75)

pom.xml

@@ -46,6 +46,7 @@
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-api</artifactId>
       <version>1.7.29</version>
+      <scope>test</scope>
     </dependency>
     <!-- antler -->
     <dependency>
@@ -78,6 +79,37 @@
     <directory>${project.basedir}/target</directory>
     <finalName>pth_03</finalName>
     <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-enforcer-plugin</artifactId>
+        <version>3.4.1</version>
+        <executions>
+          <execution>
+            <id>enforce-settings</id>
+            <goals>
+              <goal>enforce</goal>
+            </goals>
+            <configuration>
+              <rules>
+                <requireMavenVersion>
+                  <version>3.2.5</version>
+                </requireMavenVersion>
+                <requireJavaVersion>
+                  <version>[1.8,1.9)</version>
+                </requireJavaVersion>
+                <banDynamicVersions/>
+                <requirePluginVersions>
+                  <message>All plugins are required to contain specific version.</message>
+                  <unCheckedPluginList>org.apache.maven.plugins:maven-site-plugin,org.apache.maven.plugins:maven-resources-plugin,org.apache.maven.plugins:maven-clean-plugin,org.apache.maven.plugins:maven-install-plugin,org.apache.maven.plugins:maven-deploy-plugin,org.apache.maven.plugins:maven-compiler-plugin,org.apache.maven.plugins:maven-jar-plugin</unCheckedPluginList>
+                </requirePluginVersions>
+                <requireNoRepositories>
+                  <message>Do not use any external repositories.</message>
+                </requireNoRepositories>
+              </rules>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-source-plugin</artifactId>