Add build_depend on rostest

[130s]

While passes locally, catkin_make fails on hydro pre-release test:

sed -i s@/tmp/test_repositories/build_repository/devel/share@/tmp/test_repositories/src_repository/hrpsys/share@s /tmp/test_repositories/src_repository/hrpsys/share/hrpsys/samples/HRP4C//HRP4C.xml 
fix /tmp/test_repositories/build_repository/devel/lib/pkgconfig/hrpsys-base.pc
CMake Error at hrpsys/catkin.cmake:185 (add_rostest):
  Unknown CMake command "add_rostest".
Call Stack (most recent call first):
  hrpsys/CMakeLists.txt:2 (include)

Adding rostest following this qa thread.

[130s]

travis failed, but in its detailed log I can't find where the build fails...

[k-okada]

here, I always search with "catkin_make" and "filures:" to find the problem.

The test is stil unstable, so I restart the travis, see if it works.

    Start 4: _ctest_openhrp3_rostest_test_test_modelloader.test
4/8 Test #4: _ctest_openhrp3_rostest_test_test_modelloader.test ......................***Failed    2.92 sec
    Start 5: _ctest_hrpsys_rostest_test_test-hrpsys.test
5/8 Test #5: _ctest_hrpsys_rostest_test_test-hrpsys.test .............................   Passed    8.31 sec
    Start 6: _ctest_hrpsys_rostest_test_test-colcheck.test
6/8 Test #6: _ctest_hrpsys_rostest_test_test-colcheck.test ...........................   Passed    2.47 sec
    Start 7: _ctest_hrpsys_rostest_test_test-pa10.test
7/8 Test #7: _ctest_hrpsys_rostest_test_test-pa10.test ...............................   Passed    6.11 sec
    Start 8: _ctest_hrpsys_rostest_test_test-simulator.test
8/8 Test #8: _ctest_hrpsys_rostest_test_test-simulator.test ..........................   Passed    5.26 sec

88% tests passed, 1 tests failed out of 8

Total Test time (real) =  38.17 sec

The following tests FAILED:
      4 - _ctest_openhrp3_rostest_test_test_modelloader.test (Failed)
Errors while running CTest
make: *** [test] Error 8
�[31mInvoking �[1m"make"�[22m failed�[0m

The command "catkin_make test" exited with 1.
$ catkin_make install

[130s]

Hmm, this time travis passed. How come???
Anyway it should be good to merge. Thanks!