Add incomplete xml parser

Doesn't adhere to any standards. Instead, it parses what I thought was
valid xml in a haphazard way. Might still be an interesting thing to
look at, to see how one would use the parser library.

src/main/java/de/plugh/compositeparse/xml/ElementNodeParser.java

@@ -0,0 +1,51 @@
+package de.plugh.compositeparse.xml;
+
+import de.plugh.compositeparse.Block;
+import de.plugh.compositeparse.Pair;
+import de.plugh.compositeparse.ParseException;
+import de.plugh.compositeparse.Parser;
+import de.plugh.compositeparse.parsers.Decision;
+import de.plugh.compositeparse.parsers.Expression;
+import de.plugh.compositeparse.parsers.Literal;
+import de.plugh.compositeparse.parsers.Repeat;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+public class ElementNodeParser implements Parser<ElementNode> {
+
+    private static final String REGEX_NAME = "[:a-zA-Z_][:a-zA-Z0-9_.-]*";
+
+    @Override
+    public ElementNode read(Block block) throws ParseException {
+        Literal.literally("<").parse(block);
+        String name = new Expression(REGEX_NAME).parse(block);
+
+        Map<String, String> attributes = new AttributesParser().parse(block);
+
+        List<Node> subnodes = new Decision<List<Node>>(
+                // First, try to find a close tag
+                new Pair<>(
+                        block1 -> {
+                            new Repeat<>(Literal.literally(" ")).parse(block1);
+                            Literal.literally("/>").parse(block1);
+                            return null;
+                        },
+                        block1 -> new ArrayList<>()
+                ),
+                // If that fails, actually parse the contents and the rest
+                new Pair<>(
+                        Literal.literally(">"),
+                        block1 -> {
+                            List<Node> foundSubnodes = new Repeat<>(new NodeParser()).parse(block);
+                            Literal.literally("</" + name + ">").parse(block1);
+                            return foundSubnodes;
+                        }
+                )
+        ).parse(block);
+
+        return new ElementNode(name, attributes, subnodes);
+    }
+
+}