Fallback from chunked to regular uploader for small files

### Is your feature request related to a problem? Please describe.
When I run the chunked uploader on a too-small file size, I get the following:

```
boxsdk.exception.BoxAPIException: Message: File size 302023 less than minimum allowed for this API: 20000000
Status: 400
Code: file_size_too_small
```

### Describe the solution you'd like
Allow a generic upload function that falls back to the default uploading if chunked uploader refuses the file.

I realize this might be a bit high level, but considering how smooth most of the SDK is (thank you!) I feel like the folder upload (`folder.upload(path)`) is so clean and simple it would be a simple fallback for the chunked uploader.

### Describe alternatives you've considered
The alternative is a file size check, two code paths, etc.