Merge pull request #58 from nesciens/crash-adding-non-wa-chat

SIGABRT when adding non-whatsapp chat
Some memory leaks fixed.
Tested a little bit only... Feel free to revert
Revert "Some memory leaks fixed."

This reverts commit ec773c532c09f3a4dc253a1bc1ff292cb5807440.
Add a workaround for the official Android client

Since the latest release of the official WhatsApp client for Android,
random crashes occur when someone using that client starts typing a
message to a whatsapp-purple user. This seems to be related to the way
we reply to typing notices. As a workaround, disable responses to this
type of message for now.

See issue #61 for details.
README.md: Add registration/login details

Closes issue #68.
README.md: Formatting changes