Fix CI build for osx homebrew

[at-wat]

This commit fixes osx homebrew CI build by reinstalling nose to correct place.
Brew-installed numpy contains nose under numpy directory which is not in PATH.

[codecov-io]

Codecov Report

Merging #625 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #625   +/-   ##
=======================================
  Coverage   75.29%   75.29%           
=======================================
  Files          30       30           
  Lines        2882     2882           
=======================================
  Hits         2170     2170           
  Misses        712      712

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[at-wat]

OSX Build image on travis looks updated after last succeeded build.

The last succeeded build didn't contain detailed build system information. pip version was 9.0.1.
The errored build is built on:

Build image provisioning date and time
Mon Jun 25 21:55:14 GMT 2018

with pip version 10.0.1.

On errored builds, pip said:

Requirement already satisfied: nose in /usr/local/Cellar/numpy/1.14.5/libexec/nose/lib/python2.7/site-packages (1.3.7)

nose under numpy is installed by here.
This looks having been installed since a long time ago.
So, I guess some update on pip or environmental change around module searching path affected this problem.

[at-wat]

The error seems fixed by #629.