Add stars count to output of commands

Adds stars count to output of `featured`, `show`/`view`, `search`, and `stars`/`starred` commands.

Example outputs:

```
$ apm featured

Featured Atom Packages (10)
├── Zen Distraction free writing. (31244 downloads, 87 stars)
├── color-picker A Color Picker for the Atom Editor. Right click a color and select color picker to open it. (58080 downloads, 246 stars)
├── command-logger View a treemap of your Atom activity. Open from the command palette. (13129 downloads, 15 stars)
├── editor-stats Display a graph of keyboard and mouse usage for the last 6 hours. (18581 downloads, 34 stars)
├── fizzy A light-hearted, bright and bubbly syntax theme featuring bright colors, and inspired by the Espresso default highlighting, and the Soda Sublime Text 2 theme. (33983 downloads, 22 stars)
├── linter Validates your code using linters. (51451 downloads, 285 stars)
├── monokai A monokai theme (72926 downloads, 115 stars)
├── sort-lines Sorts your lines. Never gets tired. (30816 downloads, 77 stars)
├── travis-ci-status Add Travis CI status of the project to the Atom status bar.  (7481 downloads, 23 stars)
└── vim-mode Add vim modal control (40573 downloads, 64 stars)
```

```
$ apm show settings-view

settings-view
├── 0.140.0
├── https://github.com/atom/settings-view
├── Edit config settings, install packages, and change themes
├── 42039 downloads
└── 10 stars
```

cc @kevinsawicki @thedaniel