Component/upload

[meinstein]

Added two components to the Form section in quark-web. They are:

• FilePicker
• ImagePicker

Provided a short and sweet description for each in their respective READMEs

TODO:

• fix flow errors
• type the file object

[coveralls]

Coverage decreased (-1.0%) to 68.695% when pulling df43ea3 on component/upload into bc2b900 on master.

[meinstein]

I could use a hand looking at these flow errors when you have a chance. I want to make sure these components are ready so you can use them on the create modal

[AlecAivazis]

@meinstein - i addressed all of the flow errors, there were a few weird bits that I think were artifacts from the previous state when the onChange was returning a string. I also made the onChange for the components component return a list of files so the user is allowed to upload more than one file at once.