Add React base 404 page

[CodeWritingCow]

Converted 404 page from Handlebars to React component,<NotFound/>

Modified dist/index.html to load bundle.js and style.css from absolute path rather than relative path. This prevents the client from looking for those files in the wrong directory if users visit a nested route. Previously, if a user visited localhost:8080/pagenotfound/pagenotfound, React tried to load localhost:8080/pagenotfound/bundle.js instead of the correct path, localhost:8080/bundle.js.

[badwolfbit]

@CodeWritingCow there is only a stylistic issue that needs to be addressed before merging

Original:

PR #58:

[CodeWritingCow]

@omenwolf I addressed the styling issue by increasing the margin top of Parallax's content. The React 404 page looks identical to the original Handlebars page.

[badwolfbit]

@CodeWritingCow Looks great, will merge