RapClust with no params throws a stack trace

[tseemann]

It should probably show the --help instead?

% pip install rapclust
% RapClust

Traceback (most recent call last):
  File "/home/linuxbrew/.linuxbrew/bin/RapClust", line 89, in <module>
    processQuant()
  File "/home/linuxbrew/.linuxbrew/Cellar/python/2.7.12_1/lib/python2.7/site-packages/click/core.py", line 716, in __call__
    return self.main(*args, **kwargs)
  File "/home/linuxbrew/.linuxbrew/Cellar/python/2.7.12_1/lib/python2.7/site-packages/click/core.py", line 696, in main
    rv = self.invoke(ctx)
  File "/home/linuxbrew/.linuxbrew/Cellar/python/2.7.12_1/lib/python2.7/site-packages/click/core.py", line 889, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/linuxbrew/.linuxbrew/Cellar/python/2.7.12_1/lib/python2.7/site-packages/click/core.py", line 534, in invoke
    return callback(*args, **kwargs)
  File "/home/linuxbrew/.linuxbrew/bin/RapClust", line 18, in processQuant
    with open(config, 'r') as yamCfg:
TypeError: coercing to Unicode: need string or buffer, NoneType found