Fix --splinter-headless, as it could as well be of type bool, not str.

Author: mpasternak

pytest_splinter/plugin.py

@@ -237,7 +237,7 @@ def splinter_screenshot_dir(request):
 @pytest.fixture(scope="session")
 def splinter_headless(request):
  """Flag to start the browser in headless mode."""
- return request.config.option.splinter_headless == True
+ return request.config.option.splinter_headless
 
 
 @pytest.fixture(scope="session") # pragma: no cover
@@ -781,5 +781,4 @@ def pytest_addoption(parser): # pragma: no cover
  help="Run the browser in headless mode.",
  action="store_true",
  dest="splinter_headless",
- default="false",
  )