[SVCS-47] Determine MimeType During WB Dropbox Upload

[TomBaxter]

Ticket

https://openscience.atlassian.net/browse/SVCS-47

Purpose

Use python-magic(libmagic) to determine mimetypes at time of upload

Changes

update requirements.txt to include python-magic update waterbutler/core/streams/metadata.py for new class MimeStreamWriter update waterbutler/core/streams/init.py to import MimeStreamWriter update waterbutler/providers/dropbox/provider.py "def upload" to utilize MimeStreamWriter update tests/providers/dropbox/test_provider.py to use actual pdf file

ToDo: Update other providers Use "def upload" metadata return to update stored mimetype

Side effects

May be both performance and system resource issues Are uploads now slower? Does the upload process now consume additional system memory

OSF-5557

[chadwhitacre]

Punchlist

• [ ] rebase on develop
• [ ] standardize line spacing—https://github.com/CenterForOpenScience/waterbutler/pull/134#discussion_r67568847 and https://github.com/CenterForOpenScience/waterbutler/pull/134#discussion_r67573713
• [ ] explain why we only care about Dropbox—https://github.com/CenterForOpenScience/waterbutler/pull/134#discussion_r67569345
• [ ] consider consuming as little of the stream as possible—https://github.com/CenterForOpenScience/waterbutler/pull/134#discussion_r67573459
• [ ] undo spurious (whitespace?) change—https://github.com/CenterForOpenScience/waterbutler/pull/134#discussion_r67573616