webdash config

[jadjoubran]

this is required for #34 to work as expected

• [x] when you install webdash globally, you won't have any webdash.json in your project, so webdash config will generate a configuration in the current working dir
• [x] also update documentation

[jadjoubran]

this needs to be tested as a global webdash

[jadjoubran]

• [x] convert scripts/install.js into an exported method, that accepts a path
• [x] run it on install with app-root-path
• [x] run it on webdash config using process.cwd()
• [x] apply same fix to lib/config-helper.js
• [x] test using npm link