Update for head that now uses the new cloneIterable function (#353)

src/pointfree/head.js

@@ -1,8 +1,11 @@
 /** @license ISC License (c) copyright 2016 original and current authors */
 /** @author Ian Hofmann-Hicks (evil) */
 
+const isArray = require('../core/isArray')
 const isFunction = require('../core/isFunction')
 const isIterable = require('../core/isIterable')
+const isString = require('../core/isString')
+const cloneIterable = require('../core/cloneIterable')
 
 const { Nothing, Just } = require('../core/Maybe')
 
@@ -11,8 +14,13 @@ function head(m) {
     return m.head()
   }
 
+  if(isArray(m) || isString(m)) {
+    return !m.length ? Nothing() : Just(m[0])
+  }
+
   if(isIterable(m)) {
-    const iterator = m[Symbol.iterator]()
+    const cloned = cloneIterable(m)
+    const iterator = cloned[Symbol.iterator]()
     const head = iterator.next()
 
     return head.done ? Nothing() : Just(head.value)