Make the Content-Range header configurable

[bhstahl]

The JSON api supports resuming an interrupted upload. This PR changes the Content-Range header to match the resuming protocol.

Closes #11

[stephenplusplus]

Awesome, thanks! I think the linter is having problems with the semi-colons. Could you also add a couple tests? A test against the actual API would be great as well.

Also, added you to the repo. No obligations, but feel free to make 😄 changes like these in the future!

[bhstahl]

Ooop! Thanks for adding me. Will tidy this up and add tests 😄

[bhstahl]

@stephenplusplus, any ideas why the keyfile decryption is failing on the travis boxes? All tests pass locally for me (using my keyfile) with both node 0.12.14 and 4.4.4 versions.

[stephenplusplus]

Yeah, no worries about that. Travis only runs the tests after a merge to master, just to prevent abuse. Probably a good idea to split the tests into integration and unit, but haven't gotten around to that yet.

Thanks for adding the tests! I'll pull this down and test locally as soon as I can.

[stephenplusplus]

Thanks again @bhstahl!