Fix ortho projection matrix
Merge pull request #127 from csherratt/master

Fix ortho projection matrix
Added to_euler which allows moving from to and from euler coordinates.

I did not have much luck getting the old from_eular logic work the way I
expected so I updated the implementation to match my sources.

I believe this changed the order of the axis, I am unsure of what they were
before.
Merge pull request #130 from csherratt/master

Added to_euler.
Assertion macros for approximate equality

For sake of readability and consistency with the standard library macros
assert! and assert_eq!, the macros assert_approx_eq! and assert_approx_eq_eps!
have been implemented based on the ApproxEq trait.

Upon failure these macros yield readable error messages including the input
values and the tolerance (epsilon) used to determine their approximate
equality.

Resolves #131.
Update README.md to reflect item name changes

There were some outdated names presented in the readme. Fixes #128.
Merge pull request #133 from aepsil0n/readme_update

Update README.md to reflect item name changes
Merge pull request #132 from aepsil0n/approx_eq_macros

Assertion macros for approximate equality
fail! -> panic!