tweak travis build to actually test compiled Cython

.travis.yml

@@ -22,12 +22,12 @@ before_install:
   - sudo apt-get install gdb python$( python -c 'import sys; print("%d.%d" % sys.version_info[:2])' )-dbg || true
   - dpkg -l | grep gdb || true
 
-install: CFLAGS="-O2 -ggdb" pip install .
+install: CFLAGS="-O2 -ggdb -Wall -Wextra" python setup.py build_ext -i
 
 script:
   - PYTHON_DBG="python$( python -c 'import sys; print("%d.%d" % sys.version_info[:2])' )-dbg"
   - if $PYTHON_DBG -V >&2; then CFLAGS="-O0 -ggdb" $PYTHON_DBG runtests.py -vv Debugger --backends=$BACKEND; fi
-  - CFLAGS="-O0 -ggdb" python runtests.py -vv -x Debugger --backends=$BACKEND
+  - CFLAGS="-O0 -ggdb -Wall -Wextra" python runtests.py -vv -x Debugger --backends=$BACKEND
 
 matrix:
   allow_failures:
@@ -38,4 +38,3 @@ matrix:
       env: BACKEND=cpp
     - python: pypy3
       env: BACKEND=cpp      
-  fast_finish: true