Build for Java 8; upgrade dependencies and plugins (#27)

pom.xml

@@ -26,17 +26,17 @@
 
  <properties>
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
- <maven.compiler.release>7</maven.compiler.release>
- <testng.version>6.10</testng.version>
- <compiler-plugin.version>3.8.1</compiler-plugin.version>
- <surefire-plugin.version>3.0.0-M5</surefire-plugin.version>
+ <maven.compiler.release>8</maven.compiler.release>
+ <testng.version>7.5</testng.version>
+ <compiler-plugin.version>3.10.1</compiler-plugin.version>
+ <surefire-plugin.version>3.0.0-M7</surefire-plugin.version>
  <source-plugin.version>3.2.1</source-plugin.version>
- <javadoc-plugin.version>3.3.0</javadoc-plugin.version>
- <guava-agent.version>30.1.1a</guava-agent.version>
+ <javadoc-plugin.version>3.4.0</javadoc-plugin.version>
+ <guava.version>31.1-jre</guava.version>
  <gpg-plugin.version>3.0.1</gpg-plugin.version>
- <staging-plugin.version>1.6.8</staging-plugin.version>
- <release-plugin.version>3.0.0-M4</release-plugin.version>
- <apache-derby.version>10.12.1.1</apache-derby.version>
+ <staging-plugin.version>1.6.13</staging-plugin.version>
+ <release-plugin.version>3.0.0-M6</release-plugin.version>
+ <apache-derby.version>10.14.2.0</apache-derby.version>
  <skipSigning>true</skipSigning>
  </properties>
 
@@ -71,9 +71,9 @@
  <version>${apache-derby.version}</version>
  </dependency>
  <dependency>
- <groupId>com.nordstrom.tools</groupId>
- <artifactId>guava-agent</artifactId>
- <version>${guava-agent.version}</version>
+ <groupId>com.google.guava</groupId>
+ <artifactId>guava</artifactId>
+ <version>${guava.version}</version>
  </dependency>
  </dependencies>
  </dependencyManagement>
@@ -90,8 +90,8 @@
  <scope>test</scope>
  </dependency>
  <dependency>
- <groupId>com.nordstrom.tools</groupId>
- <artifactId>guava-agent</artifactId>
+ <groupId>com.google.guava</groupId>
+ <artifactId>guava</artifactId>
  </dependency>
  </dependencies>