Update math.js to include min, max, and clamp functions

Include of simple math helpers for inline calculations. All support Number types of Int and Float, but not edge case numbers such as NaN, +-infinity, or undefined.

Min: given `A` and `B` return the smaller of the two on a standard number line.

Max: given `A` and `B` return the larger of the two on a standard number line.

Clamp: given `test`, `min` and `max` return the tested value if it falls within the range of `min` and `max` such that `min < test < max` is satisfied on a standard number line.  If the constraint is not satisfied, return the closest bounding constraint.

helpers/3p/math.js

@@ -134,4 +134,61 @@ helpers.avg = function() {
   // remove handlebars options object
   args.pop();
   return exports.sum(args) / args.length;
-};
+};
+
+/**
+ * Return the min of `a` and `b`.
+ * ```handlebars
+ * {{min 1 5}}
+ * //=> '1'
+ * ```
+ *
+ * @param {Number} `a`
+ * @param {Number} `b`
+ * @api public
+ */
+
+helpers.min = function(a, b) {
+  return a < b ? a : b;
+}
+
+
+/**
+ * Return the max of `a` and `b`.
+ * ```handlebars
+ * {{max 1 5}}
+ * //=> '5'
+ * ```
+ *
+ * @param {Number} `a`
+ * @param {Number} `b`
+ * @api public
+ */
+
+helpers.max = function(a, b) {
+  return a > b ? a : b;
+}
+
+
+/**
+ * Return the value `test` constrained to the provided `min` and `max`.
+ * If the value `test` falls outside of the provided `min` or `max`, the respective bounds will be returned instead.
+ *
+ * ```handlebars
+ * {{clamp 3 2 4}}
+ * //=> '3'
+ * {{clamp 10 2 4}}
+ * //=> '4'
+ * {{clamp -10 2 4}}
+ * //=> '2'
+ * ```
+ *
+ * @param {Number} `test`
+ * @param {Number} `min`
+ * @param {Number} `max`
+ * @api public
+ */
+
+helpers.clamp = function(test, min, max) {
+  return helpers.max(min, helpers.min(text, max));
+}