Migrate changes from source-academy/cadet-frontend (#1)

* Move slang files from cadet-frontend

- Change week to chapter
- Add rttc check
- Formatting changes
  - compliance to cadet-frontend tslint rules (to be added here)
- Removed MutableVariableDeclarationError
- Context has a generic type for external properties
- Add NoDeclareMutableError, NoDeclareReservedError,
  and NoUnspecifiedOperatorError

* Add es2017 object definition

This is to prevent the TS error "Property 'entries' does not exist on
type 'ObjectConstructor'". Object.entries(...) is the offending expression, and the solution is to add a (granular) definition of the es2017 object library, where the `entries()` method was added to ES.

* Fix ts compile error for repl.ts

Error: "error TS2339: Property 'week' does not exist on type 'Context<{}>'."
This is because the Context now has the property 'chapter' instead of
'week'.

* Change github URLs to source-academy's

* Use yarn instead of npm

* Add jest (tests fail)

* Update README

* Fix yarn build throwing type errors

* Add builtins definition

- extra param for createContext
- extra param for importBuiltins
- extra param for timed (to call display from builtins)
- Have not removed the redux store call from display (now
defaultDisplay)

* Remove redux calls from default display function

Also renamed defaultDisplay -> display

* Remove import statement

* Move type BuiltIns -> interface under types

To stick to the interfaces in that file, and to consolidate the
definitions

* Add comment for typedef

* Rename BuiltIns -> CustomBuiltIns

* Fix reference lib -> dist, tsconfig compiler options for module

* Add prompt to CustomBuiltIns type

* Rename toolchain -> src, remove babel

.gitignore

@@ -1,5 +1,4 @@
 node_modules
-toolchain/*.js
-toolchain/*/*.js
+*.js
 *.map
-lib/
+dist/

README.rst

@@ -6,19 +6,18 @@ Usage
 -----
 The REPL is still under development.
 
-To install,
+To build,
 
 .. code-block::
 
-  $ git clone https://github.com/ningyuansg/slang.git
+  $ git clone https://github.com/source-academy/js-slang.git
   $ cd slang
-  $ npm install
-  $ npm run build
-  $ npm install -g
+  $ yarn
+  $ yarn build
 
-To invoke the repl, run the command `slang` anywhere:
+To invoke the repl, run the built `slang.js`,
 
 .. code-block::
 
-  $ slang
-  > 
+  $ ./slang.js
+  >