Add get_host_name method

[marvinjuette]

Add get_host_name method for easy access of the device name.

Known Issues:
Sometimes get_specifiy_host_entry returns nothing and host is empty, but this occurred only when the repeaters mac was checked.
But I already created an issue ( #74 ) because of some problems with repeaters.

[kbr]

This line is not necessary. It just binds the list callable to a new label never used later on.

[kbr]

Please never use a 'naked' except, because it will be hard to find bugs later on. Explicitly catch just the error types you expect and are able to handle.

[kbr]

Hi, thank you very much for the first pull request. The code has some issues I have commented. May I ask what kind of error you expect by calling get_specific_host_entry beside an invalid mac_address?

[kbr]

@marvinjuette you can boild down the code to

def get_host_name(self, mac_address):
    return self.get_specific_host_entry(mac_address)['NewHostName']

and leave the error-handling to the caller, who can decide what to do. Does this code return meaningfull devicenames where the other service get_generic_host_entry just returns generic names? I've not tested this so far.

[marvinjuette]

@kbr I created this method because generic_host_entry uses the index of the host in order to display all the data. And I want to get the hostname just from a mac.

[marvinjuette]

@kbr updated my code.