TST: Reduce precision requirement for test of tortuosity estimation.

[arokem]

No description provided.

[coveralls]

Coverage remained the same at 88.562% when pulling 1a6dd5a on arokem:tortuisity-test-precision into 81a3a77 on nipy:master.

[codecov-io]

Codecov Report

Merging #1231 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #1231   +/-   ##
======================================
  Coverage    86.1%   86.1%           
======================================
  Files         223     223           
  Lines       27895   27895           
  Branches     2829    2829           
======================================
  Hits        24018   24018           
  Misses       3180    3180           
  Partials      697     697

Impacted Files	Coverage Δ
dipy/reconst/tests/test_dki_micro.py	100% <100%> (ø)	⬆️
dipy/tracking/utils.py	86.89% <100%> (ø)	⬆️

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[arokem]

Interesting. These errors are new (and look unrelated!): https://travis-ci.org/arokem/dipy/jobs/229976601#L2982

[coveralls]

Coverage remained the same at 88.591% when pulling 9fa1f4b on arokem:tortuisity-test-precision into b7aa619 on nipy:master.

[coveralls]

Coverage remained the same at 88.591% when pulling 9fa1f4b on arokem:tortuisity-test-precision into b7aa619 on nipy:master.