Fixed laziness of current_user in UI modules, and added tests for current_user. #820
Fix exception in StaticFileHandler when range requested is larger than file.
Correctly handle EAGAIN when writing to PipeIOStreams

BaseIOStream._handle_write needs to catch IOError and OSError as
well as socket.error in order to handle EAGAIN when writing to a
PipeIOStream (which doesn't appear to raise socket.error when the
buffer is full).

This also provides consistency with the exceptions caught by
BaseIOStream._read_to_buffer.
Merge pull request #848 from SuprDewd/issue_820

Fixed laziness of current_user in UI modules, and added tests for current_user.
Merge pull request #851 from taguchimail/master

Correctly handle EAGAIN when writing to PipeIOStreams
Make poll timeout patchable.
Merge pull request #859 from schlamar/patch-1

Make poll timeout patchable.