Don't forget to define NDEBUG for release

Hi,

just a quick reminder before you build binaries for the 0.2 release.

Don’t forget to #define NDEBUG, which turns off asserts! Eigen is full of
asserts and so this makes a large speed difference.

I tested, and on a large molecule this made the FPS rate go from 23 to 30, a
+30% improvement.

If you are using MSVC for the windows binaries, not that MSVC’s "release mode"
automatically defines NDEBUG.

Cheers,
Benoit