Merge pull request #75 from bvssvni/expression

Upgrade to latest Rust
Merge pull request #77 from bvssvni/expression

Added Piston as dependency
Merge pull request #80 from bvssvni/expression

Return `Status` to express behaviour
Merge pull request #81 from bvssvni/expression

Fixed comment
Merge pull request #83 from bvssvni/expression

Added `Invert` decorator
Merge pull request #85 from bvssvni/expression

Added delta time for actions
Merge pull request #87 from bvssvni/expression

Added more docs for `Sequence`
Merge pull request #88 from bvssvni/expression

Fixed docs for `Wait`
Merge pull request #90 from bvssvni/expression

Added `Select` composite
Upgraded to latest Piston

* Renamed Event to Behavior
* Renamed Cursor to State