run tox on travis

.travis.yml

@@ -27,4 +27,4 @@ matrix:
 install: pip install wheel pillow pytest pdfrw pikepdf
 script:
   - python --version
-  - python -m pytest
+  - tox

setup.py

@@ -8,12 +8,6 @@ INSTALL_REQUIRES = (
     'pikepdf',
 )
 
-TESTS_REQUIRE = (
-    'pdfrw',
-    'pikepdf',
-)
-
-
 setup(
     name='img2pdf',
     version=VERSION,
@@ -44,12 +38,9 @@ setup(
     package_dir={"": "src"},
     py_modules=['img2pdf', 'jp2'],
     include_package_data=True,
-    test_suite='tests.test_suite',
     zip_safe=True,
     install_requires=INSTALL_REQUIRES,
-    tests_requires=TESTS_REQUIRE,
     extras_require={
-        'test': TESTS_REQUIRE,
         'gui': ('tkinter'),
     },
     entry_points={

tox.ini

@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py34, py35, py36, pypy, jython
+envlist = py34, py35, py36, py37, py38, pypy, jython
 skip_missing_interpreters = true
 
 [testenv]
@@ -15,4 +15,4 @@ deps =
     numpy
     scipy
 commands =
-    pytest
+    python -m pytest