Readme updates.
Merge branch 'master' of github.com:mapbox/rasterio
Merge branch 'master' of https://github.com/brendan-ward/rasterio
Merge branch 'master' of github.com:mapbox/rasterio
Merge branch 'master' of github.com:mapbox/rasterio
Merge branch 'master' of github.com:mapbox/rasterio
Add options to rio_cp for debugging #70.