Add examples directory with some common Dust implementation examples

[sethkinast]

This is a common pattern for libraries on GitHub.

• Each example should have an explanation page on dustjs.com/examples/ that links to the example.
• Each example should have a package.json or bower.json to allow it to install dependencies and Just Work™.

Some good examples could be:

• Basic Node example
• Basic Node with Express example
• Basic streaming example
• Basic browser example
• Loading Dust via AMD

[sethkinast]

Relates to #567