pathlib.Path can no be used in menpo.io
adds constrain_to_landmarks on BooleanImage
Merge pull request #440 from jabooth/iop

pathlib.Path can no be used in menpo.io
Merge pull request #441 from jabooth/booleanconstrain

adds constrain_to_landmarks on BooleanImage
add rescale_to_diagonal
tests for diagonal property
tests for rescale_diagonal
Merge pull request #442 from jabooth/rescaletodiag

add rescale_to_diagonal, diagonal property to Image
Merge remote-tracking branch 'upstream/master' into generatorrefac