Fix travis target

.travis.yml

@@ -8,18 +8,7 @@ python:
   - nightly
   - pypy
 
-install:
-  - pip install .
-  - pip install pygal_maps_world
-  - pip install pygal_maps_fr
-  - pip install pygal_maps_ch
-  - pip install pytest
-  - pip install pytest-flake8
-  - pip install pytest-cov
-  - pip install lxml
-  - pip install pyquery
-  - pip install cairosvg
-  - pip install coveralls
+install: pip install .[test]
 
 script: py.test pygal/ --flake8 --cov-report= --cov=pygal
 

setup.py

@@ -50,7 +50,8 @@ else:
     cairosvg = 'cairosvg==0.5'
 
 tests_requirements = [
-    "pyquery", "flask", cairosvg,
+    "pyquery", "flask", cairosvg, 'lxml', 'pygal_maps_world', 'pygal_maps_fr',
+    'pygal_maps_ch', 'coveralls',
     'pytest-runner', 'pytest-cov', 'pytest-flake8', 'pytest-isort',
     'pytest'
 ]
@@ -79,7 +80,7 @@ setup(
     package_data={'pygal': ['css/*', 'graph/maps/*.svg']},
     extras_require={
         'lxml': ['lxml'],
-        'png': ['cairosvg'],
+        'png': [cairosvg],
         'test': tests_requirements
     },
     classifiers=[