Implement a few nodes for the pattern matching.

src/org/nwapw/abacus/lexing/pattern/RangeNode.java

@@ -0,0 +1,18 @@
+package org.nwapw.abacus.lexing.pattern;
+
+public class RangeNode<T> extends PatternNode<T> {
+
+    private char from;
+    private char to;
+
+    public RangeNode(char from, char to){
+        this.from = from;
+        this.to = to;
+    }
+
+    @Override
+    public boolean matches(char other) {
+        return other >= from && other <= to;
+    }
+
+}