CI: run plugin tests with 2019.2 platform on travis
CI: run plugin tests with 2019.2 platform on travis

intellij-rust/intellij-rust,intellij-rust/intellij-rust,intellij-rust/intellij-rust,Undin/intellij-rust,Undin/intellij-rust,Undin/intellij-rust,Undin/intellij-rust,Undin/intellij-rust,intellij-rust/intellij-rust,intellij-rust/intellij-rust,intellij-rust/intellij-rust,Undin/intellij-rust