Fill in all packages without README.md files with a short
README.md mentioning that this is an internal Meteor package.
Break up the top paragraph of a couple of existing README.md
files to be proper long description.
There is more work to do here, involving line wrapping and the like.
'oauth' was using 'btoa', but it's not supported in IE8-9. We already
had a base64 implementation in 'ejson', so I factored it out into its
own package used by 'ejson' and 'oauth'.