Fallback to loading /usr/share/toxic/DHTservers.

First try ~/.config/tox/DHTservers, and fallback to the /usr/share
one if the former fails.

This should allow people just starting toxic for the first time to
connect to the DHT.
Update README.md
Revert that
Merge branch 'master' of https://github.com/Tox/toxic
down arrow returns empty string if at end of history
Merge pull request #82 from kl4ng/master

down arrow returns empty string if at end of history
Merge pull request #80 from viric/dhtservers

Fallback to loading /usr/share/toxic/DHTservers.