* service: Don't depend on tokio-executor
Seems to be a leftover dependency that's not used anymore.
* offchain: Upgrade hyper to 0.13, which uses tokio 0.2
* offchain: Adapt HTTP tests to Tokio 0.2
* network: Don't transitively include tokio 0.2 in WASM
1) We don't specifically depend on Tokio codec impls
2) Conflating features in Cargo means that enabling Tokio runtime
in the native environment will also do so in WASM, where it's
obviously not implemented and causes a compilation error.
* grafana-data-source: Pull hyper/tokio only in native environment
We don't use any explicit `#[lang = ...]` items anymore (`panic_fmt`
is replaced with now-stable `#[panic_implementation]`, OOM is handled
via `alloc_error_handler` directly etc.), so I thought it'd be good to
remove it for clarity to limit used nightly features.
Igor Matuszewski