Test coveralls integration

.travis.yml

@@ -4,3 +4,9 @@ rust:
   - stable
   - beta
   - nightly
+after_success: |
+  sudo apt-get install libcurl4-openssl-dev libelf-dev libdw-dev &&
+  wget https://github.com/SimonKagstrom/kcov/archive/master.tar.gz &&
+  tar xzf master.tar.gz && mkdir kcov-master/build && cd kcov-master/build && cmake .. && make &&
+  sudo make install && cd ../.. &&
+  kcov --coveralls-id=$TRAVIS_JOB_ID --exclude-pattern=/.cargo target/kcov target/debug/oxipng-*