fix: Fix error in media uploader example (#344) #342

* lay down all the boilerplate

* styles

* refactor for max customization

* document all the things

* split out utils

* tests for everything that isn't a nightmare to mock

* s3 input validation bug

* better s3 handling

* can't restart the travis build manually for some reason

* give keys more descriptive names

* add missing async

docs-src/src/examples/MediaUploader/S3.js.example

@@ -8,7 +8,7 @@
 //    fileUrl: 'https://url.of.the.file/on/s3',
 //  }
 
-<MediaUploader getS3Info={(file) => {
+<MediaUploader getS3Info={async (file) => {
   const response = await fetch(`/images/sign?file_name=${file.name}`)
   const {data} = await response.json()