add sorting features

The site would sort results by calculated score but we can give the user the option to sort by quality alone, maintenance alone, popularity or a combination maybe ??

[satazor]

There's a branch that adds this feature: https://github.com/npms-io/npms-www/tree/search-settings-url

It needs some work but is almost done. Can you try it out and give feedback?

[eyarz]

great feature!
I'm playing around with the branch and it is not really clear what should be the expected result after configuring the sorting option.
For example - if I want to sort result only by popularity, I will move the "popularity weight" to max and all the other weights to min, but the result is not sorted by popularity (from hight to low).