BUG: Fix Numpy .random.random_integer deprecation warning.

[jhlegarreta]

Fix Numpy .random.random_integer deprecation warning. Fixes:

DeprecationWarning: This function is deprecated. Please call randint(1, 20
+ 1) instead

and similar warnings.

[jhlegarreta]

The reported test failure is related to #1698.

[arokem]

I don't think it is. The error here: https://travis-ci.org/nipy/dipy/jobs/471993180#L4223 is new and looks like it's probably related to changes you made in test_mrf.py.

[jhlegarreta]

True, the additional error was caused by changes in the commit. Having a closer look at the function documentation, the lower bound is defined differently when high is omitted (0 for numpy.random.randint vs. 1 for numpy.random.random_integers), and numpy.random.randint uses half-open interval. Let's see if changes in commit 2346013 fix the difference.

[jhlegarreta]

Looks like the only error remaining now is that related to #1698.

[codecov-io]

Codecov Report

Merging #1705 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1705      +/-   ##
==========================================
- Coverage   84.26%   84.24%   -0.03%     
==========================================
  Files         114      114              
  Lines       13556    13556              
  Branches     2139     2139              
==========================================
- Hits        11423    11420       -3     
- Misses       1637     1640       +3     
  Partials      496      496

Impacted Files	Coverage Δ
dipy/reconst/forecast.py	90.15% <0%> (-2.08%)	⬇️
dipy/core/graph.py	75% <0%> (+1.19%)	⬆️

[jhlegarreta]

Ready to be merged then !

[skoudoro]

Thank you @jhlegarreta! And happy new year! 🎉 😄