[ISSUE 50] Adding in an example for multipart upload

[hannahkamundson]

What: Adding in a walkthrough example for a multipart upload Link: https://github.com/storj/uplink/issues/50

Why: There currently isn't an example of how to do a multipart upload so I had to do a lot of diggint

Please describe the tests: No tests just running it locally and verifying it works

Please describe the performance impact: N/A

Code Review Checklist (to be filled out by reviewer)

• [ ] NEW: Are there any Satellite database migrations? Are they forwards and backwards compatible?
• [X] Does the PR describe what changes are being made?
• [X] Does the PR describe why the changes are being made?
• [X] Does the code follow our style guide?
• [X] Does the code follow our testing guide?
• [X] Is the PR appropriately sized? (If it could be broken into smaller PRs it should be)
• [X] Does the new code have enough tests? (every PR should have tests or justification otherwise. Bug-fix PRs especially)
• [X] Does the new code have enough documentation that answers "how do I use it?" and "what does it do?"? (both source documentation and higher level, diagrams?)
• [ ] Does any documentation need updating?
• [X] Do the database access patterns make sense?

[hannahkamundson]

@Erikvv, let me know if you have any suggestions!

[hannahkamundson]

Okay, thank you @erikvv! I will make the changes. Do you know who has merge privileges?