Add matrix CI using Github Actions

[stiiifff]

resolve #352

[stiiifff]

GitHub Actions CI is configured but build is failing on nightly because of 1 failing test on upgrade_as_expected with error (same as with Travis CI):

---- upgrade_as_expected stdout ----
Status code: ExitStatus(ExitStatus(256))
STDOUT:     Updating 'https://github.com/rust-lang/crates.io-index' index

STDERR: Command failed due to unhandled error: Invalid manifest

Caused by: Error during execution of `cargo metadata`: error: failed to parse manifest at `/var/folders/r9/fy7r7w3x511gl63wd9pt3l980000gn/T/cargo-edit-test.mMTENrSLyuWA/Cargo.toml`

Caused by:
  failed to parse `x86_64/windows.json` as a cfg expression: invalid target specifier: unexpected character / in target name

[ordian]

@stiiifff rust-lang/cargo#7613

[killercup]

Thanks! Let's see how this goes!

bors r+

[ordian]

please remove the components here and move clippy to a separate job as well

[stiiifff]

Yep. Wondering if a separate check task is necessary as clippy does run check (https://stackoverflow.com/questions/57449356/is-cargo-clippy-a-superset-of-cargo-check)

[ordian]

what does hecrj/setup-rust-action provide compared to action-rs/toolchain?
also, it would be nice to use cache, see https://github.com/iqlusioninc/crates/blob/develop/.github/workflows/rust.yml

[stiiifff]

Mostly simplifies the install of the rustc version & components with

with:
  rust-version: stable
  components: clippy

[ordian]

I'm not sure about running nightly on all platforms, ubuntu should be enough, also we should allow it to fail