[[CHORE]] Use consistent interface for fs ops

The CLI uses the build-in Node.js `fs` module to test for the presence
of a directory in one case. In all other instances, the CLI used the
"shelljs" package. Switch to using "shelljs" consistently to better
facilitate a forthcoming removal of that package.

src/cli.js

@@ -1,7 +1,6 @@
 "use strict";
 
 var _                 = require("lodash");
-var fs                = require("fs");
 var cli               = require("cli");
 var path              = require("path");
 var shjs              = require("shelljs");
@@ -109,7 +108,7 @@ function getHomeDir() {
 
   while (paths.length) {
     homePath = paths.shift();
-    if (fs.existsSync(homePath)) {
+    if (homePath && shjs.test("-e", homePath)) {
       return homePath;
     }
   }

tests/cli.js

@@ -560,10 +560,14 @@ exports.group = {
   },
 
   testHomeRcFile: function (test) {
-    var homeRc = path.join(process.env.HOME || process.env.HOMEPATH, ".jshintrc");
+    var home = process.env.HOME || process.env.HOMEPATH;
+    var homeRc = path.join(home, ".jshintrc");
     var testStub = this.sinon.stub(shjs, "test");
     var catStub = this.sinon.stub(shjs, "cat");
 
+    // stub home directory
+    testStub.withArgs("-e", home).returns(true);
+
     // stub rc file
     testStub.withArgs("-e", homeRc).returns(true);
     catStub.withArgs(homeRc).returns('{"evil": true}');