setup CI Jenkins

[brenzi]

Please set up CI for this crate

sanity checks:

cargo build --release
cargo build --release --no-default-features
cargo build --examples
cargo test

run examples against substrate-test-node (master?) (possible with jenkins?)

[brenzi]

please also test no_std build with

cd test_no_std
cargo build

The problem is that the linker still fails for this crate....success means no duplicate lang itemerrors

[brenzi]

update: @clang fixed the linker issue in 5e7524f

[electronix]

Mostly done.

Implemented:

• Build every night a substrate-test-node (master)
• Build every night all targets (except test_no_std) of substrate-api-client
• Run examples (except contract and event_callback because of timeout) against substrate-test-node
• Cargo warning collection and visualization
• Mail notification if unstable

Remaining points are handled in #33