Make all imports relative.

This makes it possible to use imageio as a subpackage of
another library.

Note that there are some absolute imports in testing.py,
but these are only used by tests.
Fix conversion to uint8

Closes #44

New image_as_uint8() function that plugins can use to
convert image data to uint8.
trigger travis
Merge pull request #46 from almarklein/issue44

Fix conversion to uint8
FFMPEG now default

also added mkv as extension
Merge pull request #50 from imageio/movie2

FFMPEG now default
induce style error to test detection
style fail now?
style fail now?
correct style again
better handling of nan and inf in image_as_uint8
Merge pull request #51 from imageio/style

induce style error to test detection
Backport changes from v1.0+docs
Allow resources inside the package structure

We keep a special directory for local resources.
Then we can create wheels for distribution that have
the FreeImage lib and a couple of images inside this
directory.
add environment arg to disallow internet fecting. tests are aware of it
add images to wheel dist