Adds more input files

tests/README.md

+To test your code on other inputs, replace the P.input file with another file.  We have provided
+three examples for you which we will use to test your code.

tests/hashcode.input

+public static void P(String input) {
+    System.out.print(input.hashCode());
+}

tests/identity.input

+public static void P(String input) {
+    System.out.print(input);
+}

tests/sort.input

+    public static void P(String input) {
+        /* Stupid Bubble Sort! */
+        char[] array = input.toCharArray();
+        boolean swapped = true;
+        int j = 0;
+        char tmp;
+        while (swapped) {
+            swapped = false;
+            j++;
+            for (int i = 0; i < array.length - j; i++) {
+                if (array[i] > array[i + 1]) {
+                    tmp = array[i];
+                    array[i] = array[i + 1];
+                    array[i + 1] = tmp;
+                    swapped = true;
+                }
+            }
+        }
+        System.out.println(new String(array));
+    }