Move coverage fail_under to command line option instead of .coveragerc

pytest-cov randomly ignores stuff in .coveragerc; it doesn't ignore this,
but it seems cleaner to use the pytest-cov command line option anyhow.

.coveragerc

@@ -2,5 +2,4 @@
 omit = */test/*,*/windows_cmdline.py
 
 [report]
-fail_under=100
 precision=2

setup.py

@@ -92,7 +92,7 @@ def initialize_options(self):
         # adding it by default.
         # To see stdout "live" instead of capturing it, use -s.
         coverage_args = ['--cov-config', os.path.join(ROOT, ".coveragerc"), '--cov=anaconda_project',
-                         '--cov-report=term-missing', '--cov-report=html']
+                         '--cov-report=term-missing', '--cov-report=html', '--cov-fail-under=100']
         if PY2:
             # xdist appears to lock up the test suite with python
             # 2, maybe due to an interaction with coverage