Cap `bytestring' dependency

For some reason, `bytestring' versions above 0.9.2.1 causes (at least)
GHC 7.0.1 to panic, so I capped the version while investigating the
issue.
Specify and mention `cabal-install' dependency

The `cabal-install' dependency needs to be at least 1.14 so that the
build of `lifted-base' will not fail with an "unrecognized option:
--disable-benchmarks" error.
Stream.hs: Add `tryIOError', not available in `base-4.2'
Conditional dependencies for GHC 7.0.1 and README.md note
Update example for new `sendMessage' return value
pontarius-xmpp.cabal: Update `Tested-With' for new test environment

I have now finished setting up a Debian Wheezy testing environment for
building Pontarius XMPP against all GHC 7.0+ versions.
Merge pull request #34 from jonkri/master

Fix GHC 7.0 build errors, update `Tested-With', and update example