Add descriptions to package.jsons

Otherwise, npm just reads the first non-header of our readmes, which doesn't
match up accurately or cleanly (no markdown parsing).

npm-react/package.json

@@ -1,5 +1,6 @@
 {
   "name": "react",
+  "description": "React is a JavaScript library for building user interfaces.",
   "version": "0.9.0-rc1",
   "keywords": [
     "react"

package.json

@@ -1,5 +1,6 @@
 {
   "name": "react-tools",
+  "description": "A set of complementary tools to React, including the JSX transformer.",
   "version": "0.9.0-rc1",
   "keywords": [
     "react",