Fix jshint warnings in grunt/

Fixes #1052.

Test Plan:
jshint grunt

grunt/config/webdriver-all.js

@@ -110,4 +110,4 @@ module.exports = function(props){
   }
 
   return exports;
-}
+};

grunt/config/webdriver-perf.js

@@ -21,7 +21,7 @@ var params = []
   )
   .concat(reactVersions
     .map(encodeURIComponent)
-    .map(function(version){ return 'react=' + version }
+    .map(function(version){ return 'react=' + version; }
   )
 );
 

grunt/tasks/npm-react-tools.js

@@ -4,6 +4,7 @@ var fs = require('fs');
 var grunt = require('grunt');
 
 function pack() {
+  /*jshint validthis:true */
   var done = this.async();
   var spawnCmd = {
     cmd: 'npm',

grunt/tasks/npm-react.js

@@ -38,6 +38,7 @@ function buildRelease() {
 }
 
 function packRelease() {
+  /*jshint validthis:true */
   var done = this.async();
   var spawnCmd = {
     cmd: 'npm',
@@ -47,7 +48,7 @@ function packRelease() {
     }
   };
   grunt.util.spawn(spawnCmd, function() {
-    var src = 'build/react-' + grunt.config.data.pkg.version + '.tgz'
+    var src = 'build/react-' + grunt.config.data.pkg.version + '.tgz';
     var dest = 'build/react.tgz';
     fs.rename(src, dest, done);
   });