added a test for voxel_prf using the sample stimulus, response, and estimate numpy arrays downloaded via installation
small aesthetic edits to the test_voxel_prf method
added two more tests for methods in estimation module
RF: changed the print statement in the voxel_prf method
RF: there was an error in how I generated the coordinate matrices for the visual space.  instead of representing the center of each location, the coordinates represented the edge of each location.
RF: fixed another error in generate_coordinate_matrices.  now they will return the samely centered and symmetric deg_x and deg_y for any sized screens including odd or even pixels
TEST: added tests to utilities and modified some tests in estimation
RF: added a stimulus class.  this class will attempt to subsume all data attributes and subordinate functionality to a singular class model.
RF: beautification
ENH: added a base class for pRF models and fits.  also added a particular instance of the pRF models in pRF (gaussian).
RF: fixed the stimulus model so that it is a standalone model for a stimulus
Update base.py
RF: first pass at a gaussian pRF model and fit procedure
RF: removed the Stimulus class features from config
RF: beautified the execution script
RF: added popeye.stimulus to the imports
RF: removed all features that are now redundant with popeye.prf
RF: moved Stimulus specific features from popeye.utilities
RF: added test for popeye.prf and popeye.stimulus and removed redundancy from previously used tests
Modified the GaussianFit so that once its initialized through GaussianModel.fit(), the grid_search() and gradient_descent() are automatically run and the parameters are bound to the GaussianFit() object.