.coveragerc: Reenable Cython coverage plugin.

Cython coverage is only a problem when run through tox.  Disable the coverage
target in Travis Ci until this can be addressed.

Signed-off-by: Chris PeBenito <pebenito@ieee.org>

.coveragerc

@@ -1,7 +1,7 @@
 #coverage.py configuration
 [run]
 source = setools
-#plugins = Cython.Coverage
+plugins = Cython.Coverage
 
 [report]
 exclude_lines =

.travis.yml

@@ -23,11 +23,11 @@ matrix:
   fast_finish: true
   include:
     - env: TOX_ENV=pep8
-    - env: TOX_ENV=coverage
     - env: TOX_ENV=lint
+#    - env: TOX_ENV=coverage
 
-  allow_failures:
-    - env: TOX_ENV=coverage
+#  allow_failures:
+#    - env: TOX_ENV=coverage
 
 sudo: false
 dist: bionic