fix(package): add react@15 to dependencies

react@16 changes the directory structure of its package so make
sure to install react@15 otherwise users will experience module
not found errors.

Fixes #1

Author: remarkablemark

package.json

@@ -24,10 +24,16 @@
   "files": [
     "lib"
   ],
+  "dependencies": {
+    "react": "15"
+  },
+  "peerDependencies": {
+    "fbjs": "*",
+    "object-assign": "*"
+  },
   "optionalDependencies": {
     "fbjs": "*",
-    "object-assign": "*",
-    "react": "*"
+    "object-assign": "*"
   },
   "devDependencies": {
     "conventional-changelog-cli": "^1.3.3",