[skip appveyor] fix package names

.travis.yml

@@ -14,8 +14,8 @@ before_install:
   - echo $opencv_version
 
 install: 
-  - if [[ $TRAVIS_PYTHON_VERSION == 2* ]]; then sudo apt-get install libpython2.7-dev; fi
-  - if [[ $TRAVIS_PYTHON_VERSION == 3* ]]; then sudo apt-get install libpython3.5-dev; fi
+  - if [[ $TRAVIS_PYTHON_VERSION == 2* ]]; then sudo apt-get install python2.7-dev; fi
+  - if [[ $TRAVIS_PYTHON_VERSION == 3* ]]; then sudo apt-get install python3.5-dev; fi
   - python -m pip install --upgrade pip
   - pip install -r requirements.txt
   - cd opencv