Access Token support

Add accessors for an access token that is then added to the HTTP header
for all REST calls.
LBFile multipart support

Add multipart support for uploading and downloading files.
Streaming upload support

This file was accidentally left out of the earlier commit.  It supports
multipart upload/download, and now supports streaming the upload file
instead of requiring it to be in memory first.
Merge pull request #7 from sphess/master

Access Token support