Fix ordering of semvered components with a build version

## Problem
Some libraries, such as AngularJS, use odd minor version numbers for unstable versions, and even for stable version numbers. By default, we want to install the stable versions.

## Solution
My proposed solution is to sort versions containing `+` lower than those without.

## Example
The `angular` component would contain tags `v1.0.6` and `v1.1.4+`.

When `bower install angular` is run, `v1.0.6` would be installed.

To install `v1.1.4+`, a user would need to run `bower install angular#v1.1.4+`.

I'm not particularly attached to this solution, so if there are any suggestions to solve the problem differently, I'd love to hear them.

See #266 for discussion.