Update accumulo-examples to target 3.0.0-SNAPSHOT (#106)

The main branch of the accumulo-example repository should now target the
current development branch of Accumulo, which is 3.0.0-SNAPSHOT.

A 2.1 branch has been created that will continue to target the 2.1.x line of Accumulo.
diff --git a/pom.xml b/pom.xml
index ee5d26a..c97bbde 100644
--- a/pom.xml
+++ b/pom.xml
@@ -24,11 +24,11 @@
   </parent>
   <groupId>org.apache.accumulo</groupId>
   <artifactId>accumulo-examples</artifactId>
-  <version>2.1.0-SNAPSHOT</version>
+  <version>3.0.0-SNAPSHOT</version>
   <name>Apache Accumulo Examples</name>
   <description>Example code and corresponding documentation for using Apache Accumulo</description>
   <properties>
-    <accumulo.version>2.1.0-SNAPSHOT</accumulo.version>
+    <accumulo.version>3.0.0-SNAPSHOT</accumulo.version>
     <eclipseFormatterStyle>contrib/Eclipse-Accumulo-Codestyle.xml</eclipseFormatterStyle>
     <hadoop.version>3.3.4</hadoop.version>
     <maven.compiler.release>11</maven.compiler.release>