travis: Unconditionally run coveralls analysis, even if others failed.

If, for example, the code-size check failed we would still like to run the
coveralls coverage analysis.

.travis.yml

@@ -58,7 +58,7 @@ script:
   - (cd tests && MICROPY_CPYTHON3=python3.4 MICROPY_MICROPYTHON=../unix/micropython_coverage ./run-tests --emit native)
   - (cd tests && MICROPY_CPYTHON3=python3.4 MICROPY_MICROPYTHON=../unix/micropython_coverage ./run-tests --via-mpy -d basics float)
 
-after_success:
+  # run coveralls coverage analysis (try to, even if some builds/tests failed)
   - (cd unix && coveralls --root .. --build-root . --gcov $(which gcov) --gcov-options '\-o build-coverage/' --include py --include extmod)
 
 after_failure: