Merge pull request #64 from ozkriff/master

.travis.yml: Download rustc from rust-lang.org
std::cast -> std::mem
Update crate attribute.
Merge pull request #65 from luqmana/master

Update for latest rust.
Add line segment shape and functions

Create a new line segment struct that contains two Points in either
2D or 3D space.

Also create an implementation of the Intersect trait for testing
whether two line segments intersect, and where.
Merge pull request #66 from brandonw/master

Add line segment shape and functions
Updated for latest Rust