ENH: Add test examples and switch to debug mode

In the previous commit, I ran the tests in release mode and I noticed that the test #7 ctkBackTraceTest was failed only in this mode (this test was passed very well in Debug Mode).

Moreover, I added the option for testing the example to enrich this Continuous Integration of CTK

CMake/CircleCI/test.sh

@@ -12,8 +12,9 @@ mkdir /usr/src/CTK-build
 cd /usr/src/CTK-build || die "Could not cd into the build directory"
 
 cmake \
-  -DCMAKE_BUILD_TYPE:STRING=Release \
+  -DCMAKE_BUILD_TYPE:STRING=Debug \
   -DBUILD_TESTING:BOOL=ON \
+  -DCTK_BUILD_EXAMPLES:BOOL=ON \
     /usr/src/CTK || die "CMake configuration failed"
 
 make -j3 || die "examples build failed"