IMM RSS reader and dependencies

The patch I've applied below has been accepted upstream (https://bitbucket.org/k0ral/imm/pull-request/1/update-for-feed-0392-http-conduit-20-tls/diff) but not yet released to Hackage.  It is needed to build against the latest versions of these dependencies.

I've tested this by using `imm` for my RSS reading for the last few weeks.