Non-standard 1-based start position in bed files

[GWW]

Hi,

I believe the bed files emitted from this tool use a non-standard start and end position. The bed files from wgbs_tools appear to be 1-based for the start when they should be zero-based. I imagine it would be a lot of work to correct this, but it would be helpful to users to note this in the README to avoid potential downstream issues.