Hello all,

I have a raster that uses LERC compression. Opening/reading from the raster works fine, however I get the following error when trying to access the `.profile` property:
ValueError: 'LERC' is not a valid Compression

I've found that simply adding `lerc = 'LERC'` to the Compression enum in rasterio/enums.py solves this problem. Is this the correct fix and if so, would you like me to open a pull request for it?

Thanks,
Caleb