fix in readme

[romeokienzler]

IMHO the format of the config file has changed because I got te following error

python client.py
Traceback (most recent call last):
File "client.py", line 24, in
options = ibmiotf.application.ParseConfigFile("/home/pi/device.cfg")
File "/usr/local/lib/python2.7/dist-packages/ibmiotf/application.py", line 513, in ParseConfigFile
appType = parms.get(sectionHeader, "type", "standalone")
File "/usr/lib/python2.7/ConfigParser.py", line 618, in get
raise NoOptionError(option, section)
ConfigParser.NoOptionError: No option 'type' in section: 'application'

So when changing auth-method to type=apikey it works