Merge recent bug fixes of development version into v0.8.x

Update version to 0.8.1

Fix release instruction for making docs

Merge branch 'v0.7.2-prep' into v0.7.x

Conflicts:
	bento.info
	setup.py

PKG: Set version to 0.7.1.

Merge pull request scikit-image#331 from cgohlke/patch-7

DOC: Document correct parameter types.

PKG: Release 0.6.1 bugfix.

Debian release 0.6-1

PKG: Update doc versions.

Debian release 0.5.0+git100-gfeb3e92-2