Add HikariCP connection pool for MySQL (#86)

* Add HikariCP connection pool for MySQL

* Make code more compatible with connection pooling

- Remove connection caching in Process/Consumer
- Use try-with-resources to make sure Connections always get closed, even in
  when an Exception occurs.

* Disable SSL for MySQL

pom.xml

@@ -56,6 +56,10 @@
                   <pattern>org.bstats</pattern>
                   <shadedPattern>net.coreprotect</shadedPattern>
                 </relocation>
+                <relocation>
+                  <pattern>com.zaxxer</pattern>
+                  <shadedPattern>net.coreprotect</shadedPattern>
+                </relocation>
               </relocations>
             </configuration>
           </execution>
@@ -111,5 +115,10 @@
         </exclusion>
       </exclusions>
     </dependency>
+    <dependency>
+      <groupId>com.zaxxer</groupId>
+      <artifactId>HikariCP</artifactId>
+      <version>4.0.3</version>
+    </dependency>
   </dependencies>
 </project>