Use "location.assign" instead of "location ="

As it currently stands, the stable release of closure-compiler errors
out due to the use of "location = value;".

See:
https://groups.google.com/forum/#!topic/closure-compiler-discuss/sbAQr18Xe9g

According to
https://developer.mozilla.org/en-US/docs/Web/API/window.location,
`window.location` is technically read-only but lets you assign to it
using `=` anyway, to change the URL.

Because of that, this is definitely a closure-compiler issue (and was
fixed in git), but it seems like a simple enough change that can be
made in purescript-simple-dom so that the stable closure-compiler can
work with it too.

There is no functionality change at all, this simply uses `.assign()`
instead of `=` and according to the specification, they do the same thing.

Signed-off-by: Ricky Elrod <ricky@elrod.me>
Merge pull request #9 from relrod/locationfix

Use "location.assign" instead of "location ="