use GeometryTypes to replace some type

[xiuliren]

such as Point3f0 as an alternative of node
and HyperRectangle as an alternative of bounding box.

this will make package more Julia and easier to interact with other Julia packages, such as GLVisualize

[xiuliren]

changed the point/node data type to Vec, which is equivalent to Point type.
#57

the HyperRectangle was built based on starting point and size, rather than stop point.