reduce installing dependent libs for user

.travis.yml

@@ -6,6 +6,8 @@ python:
   - 3.5
   - 3.6
 install:
+  - pip install coverage
+  - pip install coveralls
   - pip install -r requirements.txt
 script:
   - coverage run --source=httprunner -m unittest discover

httprunner/__init__.py

@@ -1 +1 @@
-__version__ = '0.8.1d'
+__version__ = '0.8.2'

requirements.txt

@@ -1,6 +1,4 @@
 requests[security]
 flask
 PyYAML
-coveralls
-coverage
 PyUnitReport