Patch v0.3.4

Added a few developer experience tools to make life easier:

• Wrote a test to make sure <CheckboxField> is running this.setState in <Reforma>
• Added some flowtype annotations to <Reforma>
• Added prettier, husky, and relaxed an eslint rule so everything plays nicely together
• Upgraded Node to v8.6.0 to allow husky and lint-staged to work together nicely - Added in an .nvmrc file for nvm users to hack away 😄
• Prettified all the files! 💃💃💃💃💃💃