Add cmdline flag for easy log-config

This adds a new cmdline-flag '-L', that allows to define log-levels
for single loggers by their qualname. If you instantiate the logger
via ``logging.getLogger(__name__)``, this is the modul name, e.g.:
'pyethereum.wire'.
Add console_script for eth
Add debugging hints to README
Merge pull request #50 from brainbot-com/easy_debug

Easy debug