deprecate readsfrom/writesto in favor of simply using open on AbstractCmds, and support: open(cmd, mode) do io ... end
better rearrangement of try/catch block in open(f, cmds)
rm obsolete writesto docs
Document idx option to match.
fix convert(T<:FloatingPoint, ::Rational) to return a result of type T: was broken for convert(Float64, ::Rational{BigInt})
Merge pull request #7056 from porterjamesj/re-idx-doc

Document idx option to match.
Merge pull request #6948 from stevengj/cmdio

RFC: deprecate readsfrom/writesto in favor of simply using open on AbstractCmd