Added result sorting by downloads and/or stars

[glenntanner3]

• Was unable to add the checkboxes side-by-side, due to overlapping, thus I stacked them.
• Set most downloads as the prefered order.
• Selection change invokes search.
• Did not add a method for default selection as I do not know how to.

Description of the Change

In response to https://github.com/atom/atom.io/issues/9, this will allow the user to sort searched package/template results by downloads and/or stars value greatest to least.

Alternate Designs

Dropdown for more order combinations. Time was the primary factor in only providing checkboxes and greatest to least.

Benefits

New users will be able to determine what others are using, most popular tend to be the best maintained.

Possible Drawbacks

Newer better packages may get overlooked

Applicable Issues

Config for default sorting method wasn't implemented as I wasn't sure how to.