Execution of Maven corrected

According to #7, subprocess.call(['mvn', 'test']) doesn't work in some
cases.
This commit replaces it by call('mvn test').

Author: tcalmant

tests/tests.py

@@ -67,7 +67,7 @@ def setUpClass(cls):
         # Run Maven and go back to the working folder
         cwd = os.getcwd()
         os.chdir(java_dir)
-        subprocess.call(['mvn', 'test'], shell=True)
+        subprocess.call('mvn test', shell=True)
         os.chdir(cwd)
 
     def read_file(self, filename, stream=False):