Suggest mentioning biomformat bioc package

[seandavi]

I found this package first but then noticed that it appears that future development efforts will likely be on the Bioconductor package. It might help to find the new package by just noting its existence in the README here.

[joey711]

Thanks! deprecating and removing "biom" from CRAN has been on my to-do list for a while. Sorry for the inconvenience!