Removes spherical mean print and fixes dhollander docstring

[rutgerfick]

Closes #79 and closes #75

[coveralls]

Pull Request Test Coverage Report for Build 585

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 5 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.08%) to 82.683%

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Files with Coverage Reduction	New Missed Lines	%
dmipy/utils/tests/test_spherical_convolution.py	1	95.35%
dmipy/distributions/tests/test_bingham.py	4	89.04%

Totals
Change from base Build 581:	0.08%
Covered Lines:	4696
Relevant Lines:	5539

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💛 - Coveralls

[codecov-io]

Codecov Report

Merging #80 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #80      +/-   ##
==========================================
- Coverage   81.76%   81.76%   -0.01%     
==========================================
  Files          64       64              
  Lines        5540     5539       -1     
  Branches      653      653              
==========================================
- Hits         4530     4529       -1     
  Misses        838      838              
  Partials      172      172

Impacted Files	Coverage Δ
dmipy/utils/spherical_mean.py	100% <ø> (ø)	⬆️
dmipy/tissue_response/three_tissue_response.py	35.55% <ø> (ø)	⬆️

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