builder pattern

[clifton]

Progress:

• [x] tests/01-parse.rs
• [x] tests/02-create-builder.rs
• [x] tests/03-call-setters.rs
• [x] tests/04-call-build.rs
• [x] tests/05-method-chaining.rs
• [x] tests/06-optional-field.rs
• [ ] tests/07-repeated-field.rs
• [ ] tests/08-unrecognized-attribute.rs
• [ ] tests/09-redefined-prelude-types.rs

[clifton]

whoops! sorry about that was just trying to make a pull request to my fork