Randomize tests again

this used to be enabled, but the plugin changed how it works
> From v1.0.0 onwards, this plugin no longer randomises tests by default.

.travis.yml

@@ -19,7 +19,6 @@ addons:
 install:
 - cd build_helpers && ./install_ta-lib.sh; cd ..
 - export LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH
-- pip install --upgrade pytest-random-order
 - pip install -r requirements-dev.txt
 - pip install -e .
 jobs:
@@ -27,7 +26,7 @@ jobs:
   include:
     - stage: tests
       script:
-      - pytest --cov=freqtrade --cov-config=.coveragerc freqtrade/tests/
+      - pytest --random-order --cov=freqtrade --cov-config=.coveragerc freqtrade/tests/
       # Allow failure for coveralls
       - coveralls || true
       name: pytest

requirements-dev.txt

@@ -9,5 +9,6 @@ pytest==5.0.0
 pytest-mock==1.10.4
 pytest-asyncio==0.10.0
 pytest-cov==2.7.1
+pytest-random-order==1.0.4
 coveralls==1.8.1
 mypy==0.711