MAINTENANCE fix deploing codecoverage data on Travis CI

Go to the correct directory with codecov.yml before sending data
to codecov server.
diff --git a/.travis.yml b/.travis.yml
index 195b20a..19cd203 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -31,6 +31,7 @@
 
 script:
   - mkdir build && cd build && cmake .. && make -j2 && ctest --output-on-failure
+  - cd -
 
 after_success:
   - if [ "$TRAVIS_OS_NAME" = "linux" -a "$CC" = "gcc" ]; then codecov; fi