Update build; improve caching; improve tests

fixtures/repositories/m2/com/github/anuken/packr/maven-metadata.xml

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<!--
+  ~ Copyright 2020 the original author or authors.
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~      http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+
+<metadata modelVersion="1.0.0">
+    <groupId>com.github.anuken</groupId>
+    <artifactId>packr</artifactId>
+    <versioning>
+        <release>packr-1.2</release>
+        <versions>
+            <version>packr-1.2</version>
+        </versions>
+    </versioning>
+</metadata>