add server side timestamp
append mode should be specified at initialization time

It doesn't work to have append mode as an argument to write. This is now deprecated.
add batch writing support to collections
avoid potential ts collision
reliable downloading for collections and job data
reverse use of requests_params and apiparams.

Although less consistent with lower-level API, it is consisent with collections API and more user friendly.
stream large downloads
fix bug with combining a start parameter with download retries
switch to secure endpoint
revert to http endpoint while we debug hangs on https
add max_retries option to HubstorageClient
fix merge conflict

Conflicts:
	hubstorage/client.py