Install libssh2 on macOS

Author: JohnTitor

ci/run.sh

@@ -23,6 +23,8 @@ case "${TRAVIS_OS_NAME}" in
         TEST_TARGET=x86_64-pc-windows-msvc cargo test --verbose -- --nocapture
         ;;
     *"macos"*)
+        # Needs for travis.
+        brew install libssh2
         TEST_TARGET=x86_64-apple-darwin cargo test --verbose -- --nocapture
         ;;
 esac