Fix CI (finally) (#265)

* Update some deps

Signed-off-by: koushiro <koushiro.cqx@gmail.com>

* Format

Signed-off-by: koushiro <koushiro.cqx@gmail.com>

* Fix clippy-wasm

Signed-off-by: koushiro <koushiro.cqx@gmail.com>

* [examples] fix minor formatting issues

* [examples] fix some clippy warnings

* [lang2/macro] silence warning for ink! constructors named "new"

* [*] replace documentation link in Cargo.toml to ink! tutorial

* [abi] specify allow(clippy::trivially_copy_pass_by_ref) in a smaller scope

* [abi] specify allow(clippy::new_ret_no_self) in smaller scope

* [ci] adjust gitlab-ci.yml

* [ci] update Travis CI to just do coverage reporting