Remove maven-shade-plugin to publish original pom (#132)

The shade-plugin alters the pom.xml removing runtime dependencies.
This makes that components consuming asciidoclet cannot resolve required
dependencies like AsciidoctorJ, causing conversion to fail.

closes #120

pom.xml

@@ -94,7 +94,6 @@
                         <mavenExecutorId>forked-path</mavenExecutorId>
                     </configuration>
                 </plugin>
-                <!-- default plugins for build, if not defined in parent-pom -->
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-resources-plugin</artifactId>
@@ -242,23 +241,6 @@
                     <strictCheck>true</strictCheck>
                 </configuration>
             </plugin>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-shade-plugin</artifactId>
-                <version>3.5.2</version>
-                <configuration>
-                    <shadedArtifactAttached>true</shadedArtifactAttached>
-                    <shadedClassifierName>shaded</shadedClassifierName>
-                </configuration>
-                <executions>
-                    <execution>
-                        <phase>package</phase>
-                        <goals>
-                            <goal>shade</goal>
-                        </goals>
-                    </execution>
-                </executions>
-            </plugin>
         </plugins>
     </build>