Update dependencies: grpc-java, protobuf, gson, slf4j, guava, junit (#27)

Author: njhill

pom.xml

@@ -55,14 +55,14 @@
    </distributionManagement>
 
    <properties>
-      <grpc-version>1.25.0</grpc-version>
+      <grpc-version>1.26.0</grpc-version>
       <netty-version>4.1.42.Final</netty-version>
       <netty-tcnative-version>2.0.26.Final</netty-tcnative-version>
-      <protoc-version>3.10.0</protoc-version>
-      <gson-version>2.8.5</gson-version>
-      <slf4j-version>1.7.29</slf4j-version>
-      <junit-version>4.12</junit-version>
-      <guava-version>28.1-jre</guava-version>
+      <protoc-version>3.11.0</protoc-version>
+      <gson-version>2.8.6</gson-version>
+      <slf4j-version>1.7.30</slf4j-version>
+      <junit-version>4.13</junit-version>
+      <guava-version>28.2-jre</guava-version>
       <annotation-version>1.3.2</annotation-version>
 
       <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>