* add brightness and contrast augmentation
* remove unnecessary
* reformat
* relax the precision constrain for adjust_brightness aug
* fix percision assertion error in unit test
* remove toy
* rename alpha as factor
* use np.testing.assert_allclose in place of np.less_equal
* add equalize augmentation in mmcv
* delete unnecessary
* reformat
* remove clip in implementing equalize, and add uint test with case step=0
* remove clip in implementing equalize, and add uint test with case step=0
* add comments for unit test
* rename function name as imequalize
* add Color augmentation
* reformat
* reformat
* reformat docstring
* reformat docstring
* add more unit test
* add more unit test
* add clip value and uint test for image with type float
* rename function name