Merge pull request #15 from source-academy/type-fix

Move @types/acorn and @types/estree to dependencies

Author: remo5000

package.json

@@ -7,6 +7,8 @@
     "url": "https://github.com/source-academy/"
   },
   "dependencies": {
+    "@types/acorn": "^4.0.3",
+    "@types/estree": "0.0.39",
     "acorn": "^5.7.1",
     "astring": "^1.2.0",
     "commander": "^2.14.1",
@@ -32,9 +34,7 @@
   },
   "homepage": "https://github.com/source-academy/js-slang",
   "devDependencies": {
-    "@types/acorn": "^4.0.3",
     "@types/common-tags": "^1.4.0",
-    "@types/estree": "0.0.39",
     "@types/invariant": "^2.2.29",
     "@types/jest": "^23.1.4",
     "@types/node": "^9.4.7",