Fix exception in StaticFileHandler when range requested is larger than file.
RequestHandler sets its close callback on the HTTPConnection, not the IOStream.

Fixes a bug in which close callbacks would never be called for subsequent
requests on a reused connection.
Add 3.1.1 release notes.
Set version number to 3.1.1
Merge Tornado v3.1.1 (commit 'f36652d47fc42205c085ed65e740f4b155d4e5e4') into streambody