Fix Maven warnings

pom.xml

@@ -22,6 +22,10 @@
     <connection>https://github.com/scrosby/OSM-binary.git</connection>
   </scm>
 
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+  </properties>
+
   <build>
 	<sourceDirectory>${basedir}/src.java</sourceDirectory>
     <outputDirectory>${basedir}/build</outputDirectory>
@@ -32,6 +36,7 @@
 	  <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-compiler-plugin</artifactId>
+        <version>3.8.1</version>
         <configuration>
           <source>1.8</source>
           <target>1.8</target>
@@ -42,6 +47,9 @@
         <groupId>org.xolstice.maven.plugins</groupId>
         <artifactId>protobuf-maven-plugin</artifactId>
         <version>0.6.1</version>
+        <configuration>
+          <protocExecutable>protoc</protocExecutable>
+        </configuration>
         <executions>
           <execution>
             <id>generate-sources</id>