Test modification for windows 10 / numpy 1.14

[skoudoro]

This PR is a correction for test_dti.py which is failing on windows 10 / numpy 1.14

The arrays seems to be different on the 14nth decimal place. This is really strange.

This problem does not appear on linux.

[coveralls]

Coverage remained the same at 85.332% when pulling ee0f2f2 on skoudoro:windows-10-test-dti into 7311acc on nipy:master.

[coveralls]

Coverage remained the same at 85.332% when pulling ee0f2f2 on skoudoro:windows-10-test-dti into 7311acc on nipy:master.

[codecov-io]

Codecov Report

Merging #1336 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #1336   +/-   ##
=======================================
  Coverage   87.02%   87.02%           
=======================================
  Files         228      228           
  Lines       28841    28841           
  Branches     3100     3100           
=======================================
  Hits        25098    25098           
  Misses       3037     3037           
  Partials      706      706

Impacted Files	Coverage Δ
dipy/reconst/tests/test_dti.py	99.6% <100%> (ø)	⬆️

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[Garyfallidis]

Cool, thanks.