Update Documentation

[vlilanl]

Updated documentation for ReadsQC in README and index.rst

For the README, do I still need this:

## Required Database

* [RQCFilterData Database](https://portal.nersc.gov/cfs/m3408/db/RQCFilterData.tgz): It is a 106G tar file includes reference datasets of artifacts, adapters, contaminants, phiX genome, host genomes.  

* Prepare the Database

bash
	mkdir -p refdata
	wget https://portal.nersc.gov/cfs/m3408/db/RQCFilterData.tgz
	tar xvzf RQCFilterData.tgz -C refdata
	rm RQCFilterData.tgz

[aclum]

Looks good. Thanks!