add range header to Bitbucket download method
add range header to Bitbucket download method

 * Bitbucket doesn't support the Range header, but perhaps one day it
   will.  Draw attention to this fact by including it in the
   download() signature and documenting it in the Quirks.  Start
   passing the Range header to the Bitbucket v1 download endpoint.
   BB's v2 API was tested locally and also does not support the Range
   header.

RCOSDP/waterbutler,CenterForOpenScience/waterbutler,felliott/waterbutler