Update readme.md

Added libtelldus-core-dev. You at least needs this on Debian.
Merge pull request #53 from olekenneth/patch-1

Update readme.md
A small typo in the getDevices example
Merge pull request #55 from jdagerot/master

A small typo in the getDevices example
Fel i readme.md

fel i exempel för telldus.addDeviceEventListener
Merge pull request #56 from hugosp/patch-1

Fel i readme.md