ENH Better error messages for JPEG

Instead of a generic error, use jpeglib mechanisms to get error and
report it to Python.
BLD Use setuptools for building

We also need to install numpy *before* building as building requires
numpy. This should make imread friendlier to anaconda.
BLD Include numpy explicitly

This is analogous to the fix here:

https://github.com/luispedro/mahotas/pull/45
DOC Add installation instructions
BLD New release 0.4

Better building infrastructure is the killer feature.

Full ChangeLog:
	* Add configuration for TIFF saving
	* Correctly save 16 bit PNG images
	* Better error messages for JPEG
Manual merge from upstream master