implement a converter between the geotypes from different versions.

## geo-types

* BREAKING: Remove deprecated functions on the `Geometry<T>`:
  * `into_point` - Switch to `std::convert::TryInto<Point>`
  * `into_line_string` - Switch to `std::convert::TryInto<LineString>`
  * `into_line` - Switch to `std::convert::TryInto<Line>`
  * `into_polygon` - Switch to `std::convert::TryInto<Polygon>`
  * `into_multi_point` - Switch to `std::convert::TryInto<MultiPoint>`
  * `into_multi_line_string` - Switch to `std::convert::TryInto<MultiLineString>`
  * `into_multi_polygon` - Switch to `std::convert::TryInto<MultiPolygon>`
* BREAKING: Remove deprecated `CoordinateType` trait. Use `CoordFloat` or `CoordNum` instead.
* BREAKING: Remove deprecated functions from `LineString<T>`
  * Remove `points_iter()` -- use `points()` instead.
  * Remove `num_coords()` -- use `geo::algorithm::coords_iter::CoordsIter::coords_count` instead.
* BREAKING: Remove deprecated functions from `Point<T>`
  * Remove `lng()` -- use `x()` instead.
  * Remove `set_lng()` -- use `set_x()` instead.
  * Remove `lat()` -- use `y()` instead.
  * Remove `set_lat()` -- use `set_y()` instead.
* BREAKING: Remove deprecated `Polygon<T>::is_convex()` -- use `geo::is_convex` on `poly.exterior()` instead.
* BREAKING: Remove deprecated `Rect<T>::try_new()` -- use `Rect::new` instead, since `Rect::try_new` will never Error. Also removes corresponding `InvalidRectCoordinatesError`.

## geo

* BREAKING: Remove deprecated `rotate()` from the `Rotate` trait:
> Equivalent to `rotate_around_centroid` except for `Polygon<T>`, where it is equivalent to rotating around the polygon's outer ring. Call that instead, or `rotate_around_center` if you'd like to rotate around the geometry's bounding box center.
* BREAKING: Remove `ToGeo` trait. Switch to `std::convert::Into<Geo>` or `std::convert::TryInto<Geo>`.