Computed class properties (#4500)

* Support computed class property names (#4499)

** Depends on babel/babylon#121 **

* `babel-types`: Add `computed` field to `ClassProperty`

* `babel-plugin-transform-class-properties`: handle computed property names correctly

* `babel-generator`: add tests for class properties (computed/literal, static/instance)

* doc: Update babel-types with ClassProperty.computed

* chore(package): update babylon to v6.11.0

* babel-types: move ClassProperty.computed to be last builder arg

packages/babel-plugin-transform-class-properties/test/fixtures/general/instance-computed/actual.js

@@ -0,0 +1,3 @@
+class Foo {
+  [bar] = "foo";
+}

packages/babel-plugin-transform-class-properties/test/fixtures/general/instance-computed/expected.js

@@ -0,0 +1,4 @@
+var Foo = function Foo() {
+  babelHelpers.classCallCheck(this, Foo);
+  this[bar] = "foo";
+};