Adding more info to the README.md page

README.md

@@ -2,4 +2,15 @@
 Thousands of high-quality analyzed methylomes.
 
 If you would like to suggest a publicly available methylome for
-inclusion in methbase, please submit an issue [here](https://github.com/smithlabcode/methbase/issues).
+inclusion in methbase, please submit an issue
+[here](https://github.com/smithlabcode/methbase/issues).
+
+The methbase database includes many more methylomes than are available
+for viewing with the methbase track hub. Those selected for the track
+hub meet criteria that help ensure they have been analyzed correctly.
+
+Currently the criteria are:
+
+- 0.9: Minimum bisulfite conversion rate.
+- 1.0: Minimum average coverage across the genome.
+- 0.8: Minimum fraction of CpG sites covered.