Add retries to the Upload resource

[jsh2134]

When doing an import with 50 files, I used the import shortcut. On the 44th upload the connection to upload was aborted and I have to start again.

Having the upload endpoint retry multiple times would greatly improve this workflow.

Total time elapsed: 00:01:07
Successfuly uploaded file vt.exac.decomposed.normalized.vcf.gz.044.json.gz (id:432432806254611136 size:97631659 md5:761267ce7102cdf6bad111642af0dda0)
Uploading file: vt.exac.decomposed.normalized.vcf.gz.001.json.gz
[ 77 %] Time elapsed: 00:03:40 | ETA: 00:01:03

[100 %] Time elapsed: 00:07:39 | ETA: 00:00:00
Total time elapsed: 00:07:39
Traceback (most recent call last):
  File "/Users/ganesha/.virtualenvs/sbdp/bin/solvebio", line 11, in <module>
    load_entry_point('solvebio', 'console_scripts', 'solvebio')()
  File "/Users/ganesha/code/solve/solvebio-python/solvebio/cli/main.py", line 231, in main
    return args.func(args)
  File "/Users/ganesha/code/solve/solvebio-python/solvebio/cli/data.py", line 120, in import_file
    manifest.add(*args.file)
  File "/Users/ganesha/code/solve/solvebio-python/solvebio/resource/manifest.py", line 69, in add
    self.add_file(path)
  File "/Users/ganesha/code/solve/solvebio-python/solvebio/resource/manifest.py", line 29, in add_file
    upload = solvebio.Upload.create(path=path)
  File "/Users/ganesha/code/solve/solvebio-python/solvebio/resource/upload.py", line 112, in create
    headers=headers)
  File "/Users/ganesha/.virtualenvs/sbdp/lib/python2.7/site-packages/requests/api.py", line 124, in put
    return request('put', url, data=data, **kwargs)
  File "/Users/ganesha/.virtualenvs/sbdp/lib/python2.7/site-packages/requests/api.py", line 56, in request
    return session.request(method=method, url=url, **kwargs)
  File "/Users/ganesha/.virtualenvs/sbdp/lib/python2.7/site-packages/requests/sessions.py", line 488, in request
    resp = self.send(prep, **send_kwargs)
  File "/Users/ganesha/.virtualenvs/sbdp/lib/python2.7/site-packages/requests/sessions.py", line 609, in send
    r = adapter.send(request, **kwargs)
  File "/Users/ganesha/.virtualenvs/sbdp/lib/python2.7/site-packages/requests/adapters.py", line 473, in send
    raise ConnectionError(err, request=request)
requests.exceptions.ConnectionError: ('Connection aborted.', error(32, 'Broken pipe'))