Changes to send data from Graphite to Zabbix

This also creates the required elements (hosts, items, triggers etc) in Zabbix based on definitions from users.
An idiom which handles clean-up (such as `fin.close()`) automatically is Python's [with](http://legacy.python.org/dev/peps/pep-0343/) statement. E.g.:
````
with open("/tmp/t") as my_file:
  raise IOError("Something unrelated happened here.")
  for line in my_file:
    # do more
    pass
````
Here `my_file` is closed and not a dangling file handle.