Make std crate feature default for all ink crates (#146)

* make std crate feature default for all ink crates

* adjust travis CI for builds without std feature enabled

* remove incorrect usages of ink_abi

* apply rustfmt

* remove invalid type-metadata dependencies for ink_core

* [lang] fix Cargo.toml indentations

* adjust Erc20 token examples for new std crate feature

* adjust template and lang example std feature and propagation