Create <template> items with `lx create`

[chriskrycho]

I want to be able to type lx create post --draft or lx create page or lx create poem or whatever else I define, and have it generate a custom template with the relevant bits pre-populated.

• [ ] get list of templates in source directory (from config)
• [ ] match to template specified or default (from config)
• [ ] generate the new file (#17)