FreeImage manitenance

Hi all, Apropos of the recent discussion about and troubles with diagnosing FreeImage library loading problems on 64-bit windows, I have tried to enhance the library-loading code: https://github.com/scikits-image/scikits-image/pull/117 And speaking of FreeImage and 64-bit-ness, https://github.com/scikits-image/scikits-image/pull/112 fixes some problems in 64-bit image loading, and also clarifies how to deal with 64-bit pointers and the ctypes interface. Finally, https://github.com/scikits-image/scikits-image/pull/113 builds on the changes in PR 112 to expose basic image metadata reading in a 64-bit-safe manner. Comments welcome. Zach