[guides] URL-encode spaces (%20) in links
[guides] URL-encode spaces (%20) in links

When markdown files have spaces in their names, we need to URL-encode those spaces in links to them.
exponentjs/exponent,exponentjs/exponent,exponent/exponent,exponent/exponent,exponent/exponent,exponentjs/exponent,exponentjs/exponent,exponent/exponent,exponentjs/exponent,exponentjs/exponent,exponent/exponent,exponentjs/exponent,exponent/exponent,exponent/exponent,exponentjs/exponent,exponentjs/exponent,exponent/exponent,exponent/exponent