Bump version 0.9.0b1
Require tornado>=3.0.

Re: ArchiveTeam/seesaw-kit#55
externalprocess.py: Add AsyncPopen2 adapter and use it for ExternalProcess

Closes ArchiveTeam/seesaw-kit#55
externalprocess_test: Decode data as UTF-8 as output is always binary now
templates: Remove redundant escape()s
externalprocess: Set exit callback last to avoid hang
Merge branch 'development'

Conflicts:
	seesaw/__init__.py
Release version 0.8.1