Improve cli documentation

- Changes to documentation to make it more concise
- Improve installation steps documentation
- Surface available commands and mostly used options
  
```
$ origami-build-tools
```
Now outputs:

```
Usage: origami-build-tools <command> [<options>]

Commands:
   install  Install system and local dependencies
   build    Build module in current directory
   demo     Build demos into the demos/ directory
   verify   Lint code and verify if module structure follows the Origami specification
   test     Test if Sass silent compilation follows the Origami specification
   docs     Build module documentation into the docs/ directory

Mostly used options include:
   [--watch]                    Re-run every time a file changes
   [--local]                    Build demos locally, and preview them in a browser
   [--updateorigami]            Update origami.json with the latest demo files created
   [--js=<path>]                Main JavaScript file (default: ./src/main.js)
   [--sass=<path>]              Main Sass file (default: ./src/main.scss)
   [--buildJs=<file>]           Compiled JavaScript file (default: main.js)
   [--buildCss=<file>]          Compiled CSS file (default: main.css)
   [--buildFolder=<dir>]        Compiled assets directory (default: ./build/)
   [--scssLintPath=<path>]      Custom scss-lint configuration
   [--jsHintPath=<path>]        Custom JS Hint configuration
   [--editorconfigPath=<path>]  Custom .editorconfig

Full documentation: http://git.io/bBjMNw
```
Two things. This isn't part of the origami.json but part of the config.json in the demos folder. And the output is just the demos key of that config.json