Document how to add a new image reader
Merge pull request #8 from rsrock/master

Documentation for creating new image readers
IO: allow dynamic loading of file formats
Add a dummy file format to test dynamic loading
Added Andor SIF reader
Register SIF reader in io.jl
Doc formatting
SIF imread now sees the AndorSIF type from Images
Docs now cover the change to the imread call to find the image type
Merge pull request #9 from rsrock/master

IO: Andor SIF