Add List.insert and upgrade Immutable.js

This commit upgrades Immutable to 3.8.1, and sets it to `>=` in
`package.json`.

It also adds a `List.insert()` method to typed-immutable lists.

FIxes #20.

package.json

@@ -35,7 +35,7 @@
  "prepublish": "npm run build"
  },
  "dependencies": {
- "immutable": "3.7.0"
+ "immutable": ">=3.8.1"
  },
  "devDependencies": {
  "babel": "5.6.14",

src/list.js

@@ -130,7 +130,7 @@ class TypeInferedList extends BaseImmutableList {
  }
 
  get(index, notSetValue) {
- return this[$store] ? this[$store].get(index, notSetValue) :
+ return this[$store] ? this[$store].get(parseInt(index), notSetValue) :
  notSetValue
  }
 
@@ -142,13 +142,27 @@ class TypeInferedList extends BaseImmutableList {
  return this[$empty] || this[$read]()
  }
 
+ insert(index, value) {
+ if (index > this.size) {
+ throw TypeError(`Index "${index}" is out of bounds.`)
+ }
+
+ const result = this[$type][$read](value)
+
+ if (result instanceof TypeError) {
+ throw TypeError(`Invalid value: ${result.message}`)
+ }
+
+ return change(this, store => store.insert(index, value))
+ }
+
  remove(index) {
  return change(this, store => store && store.remove(index))
  }
 
  set(index, value) {
  if (index > this.size) {
- throw TypeError(`Index "${index}" is out of bound`)
+ throw TypeError(`Index "${index}" is out of bounds.`)
  }
 
  const result = this[$type][$read](value)

src/test/list.js

@@ -545,6 +545,17 @@ test('push inserts at highest index', assert => {
  assert.deepEqual(v1.toArray(), [1, 2, 3, 4, 5, 6])
 })
 
+test('insert inserts where told', assert => {
+ const v0 = NumberList.of(1, 2, 3, 4, 5)
+ const v1 = v0.insert(2, 50)
+
+ assert.ok(v0 instanceof NumberList)
+ assert.ok(v1 instanceof NumberList)
+
+ assert.deepEqual(v0.toArray(), [1, 2, 3, 4, 5])
+ assert.deepEqual(v1.toArray(), [1, 2, 50, 3, 4, 5])
+})
+
 test('pop removes the highest index, decrementing size', assert => {
  const v0 = NumberList.of(1, 2, 3)
  const v1 = v0.pop()