Update nalgebra to fix compilation error on Rust 1.40

[Julian-Wollersberger]

In Rust 1.40 a future-compatibility-warning will become a hard error, which will cause the dependency nalgebra v0.17.2 to no longer compile.
Reason: Rust 2015: No longer downgrade NLL errors

rust-sloth$ cargo +nightly check
    Checking nalgebra v0.17.2
error[E0502]: cannot borrow `*self` as immutable because it is also borrowed as mutable
   --> /home/myname/.cargo/registry/src/github.com-1ecc6299db9ec823/nalgebra-0.17.2/src/base/cg.rs:297:44
    |
297 |                 self[(j, i)] += shift[j] * self[(D::dim() - 1, i)];
    |                 ---------------------------^^^^-------------------
    |                 |                          |
    |                 |                          immutable borrow occurs here
    |                 mutable borrow occurs here
    |                 mutable borrow later used here

error: aborting due to previous error

For more information about this error, try `rustc --explain E0502`.
error: could not compile `nalgebra`.

To learn more, run the command again with --verbose.

To fix this, I ran cargo update --package nalgebra to update it to v0.17.3.
(Just cargo update causes the terminal renderer to mess up...)

Btw, this project is amazing ^^
I've made a bash alias pikachu and I show it to basically every IT person I meet :)

[ecumene]

WOW This PR is OLD, and I'm sorry.

Looks good to me, there's another PR that does the exact same thing. They ran cargo fmt on the code (which I didn't) but I don't really like how it mangles my meticulously written linear algebra!!!

Well done!

[Julian-Wollersberger]

WOW This PR is OLD

Time flys by, doesn't it! :)