Node.js changes
Express fixes
Add-on Credential edits
Node.js guides edits
Line folding
Express guide edits
Review Node.js Hello World app
Review Add-on credentials on Node.js
Express link points to dev-center instead of github
Fixes for improved consistency with other guides
Code snippet edits
Formatting fixes for consistency
Final review fixes
Merge pull request #97 from cloudControl/nodejs_final

Node.js guides (Add-on credentials, Express App and Hello World App)