Remove redundant method

[hvgazula]

nobrainer/nobrainer/processing/segmentation.py

Lines 41 to 44 in 902a124

	def add_model(self, base_model, model_args=None):
	"""Add a segmentation model"""
	self.base_model = base_model
	self.model_args = model_args or {}

I forgot to delete this when unrolling the changes from #303 (comment)