ENH: Bump version to 4.4.0. (#13)

Keep in sync with the ITK version.

Change-Id: I587cbb65ec9cf3449da8ecf715559cf865aa9ab2
ENH: Bump ITK superbuild to 4.3.1.

Latest stable tag.

Change-Id: Ib44ab82752ebdbb763683e1ba82bb700063cf809
Merge topic 'VersionBump' into master

7a180996 ENH: Bump ITK superbuild to 4.3.1.
b8ce41d3 ENH: Bump version to 4.4.0. (#13)