Use simpler location blocks

there's no need for a regex match for the url `/index.html`

Use prefix-matching for assets as that's the nginx-way® and the rule is simpler.

Note that this isn't the case on istlsfastyet.com:

> make sure you are using cache busting filenames or query params
> The problem is, most people will just copy/paste the snippets and never think about it twice

I can probably help with that - Paul created h5bp/server-configs-nginx#44 which is what brought this repo to my attention.

Using url suffix matches isn't without it's problems - it makes it impossible to serve a dynamic file with any of those file extensions e.g. (randomly googled example) [this wouldn't work](http://stackoverflow.com/questions/12982620/how-to-serve-static-files-css) as the url `/cards.css` wouldn't reach the application (unless ruby was also the 404 handler). IMO that's a greater problem - and arguably more likely to occur.

Expressed differently: I think it's a bit of a disservice to use what is considered a poor practice by many to accomodate copy and paste users.

There are 3 things which currently stand out in the nginx.conf file in this repo as in need of addressing:

 * [a malformed regex](https://github.com/igrigorik/istlsfastyet.com/blob/master/nginx.conf#L70)
 * [unnecessary url suffix matches](https://github.com/igrigorik/istlsfastyet.com/blob/master/nginx.conf#L65)
 * [using a redirect based on hostname](https://github.com/igrigorik/istlsfastyet.com/blob/master/nginx.conf#L60-L62)

The first looks like a typo since there is no escape sequence `\i`, the other two are likely to be considered bad practices by more competent nginx users than myself.

In conclusion then: remote the asset rule change and just fix the index location block? it's just a one char change if you only want to correct the regex to be valid.