Add Nodemailer and Mailgun option for contact form

package.json

@@ -19,6 +19,7 @@
     "less": "~1.6.2",
     "mongoose": "~3.8.5",
     "node-foursquare": "~0.2.0",
+    "nodemailer": "~0.6.0",
     "passport": "~0.2.0",
     "passport-facebook": "~1.0.2",
     "passport-github": "~0.1.5",
@@ -27,7 +28,6 @@
     "passport-oauth": "~1.0.0",
     "passport-twitter": "~1.0.2",
     "request": "~2.33.0",
-    "sendgrid": "~0.4.6",
     "tumblr.js": "~0.0.4",
     "twit": "~1.1.12",
     "underscore": "~1.5.2",