Add debian jessie (testing) to supported distros.
Upgrade to Ruby 2.0 p195
Install lzma compression library for Ag
Update Ruby version to 2.0.0-p247

* Security fix release notes: http://www.ruby-lang.org/en/news/2013/06/27/ruby-2-0-0-p247-is-released/
* Also, Heroku is now running the same patchlevel. Maintains dev/prod parity
Switch Thin to Unicorn

As the Rails application scales to more Heroku dynos, a lack of
concurrency can result in [poor performance][1] and an over-provisioning
of resources. Modifying the app to handle requests more efficiently is
a simple process with immediate benefits.

Unicorn is a [concurrent web server][2] that spawns several processes
within a single dyno without requiring concurrency or threading
awareness in your app.  Applications that migrate to Unicorn often
require fewer dynos and see increased performance.

[1]: https://blog.heroku.com/archives/2013/2/16/routing_performance_update
[2]: https://blog.heroku.com/archives/2013/2/27/unicorn_rails
Use standalone `hub`, not RubyGems version

https://gist.github.com/defunkt/284823
Remove .zshrc stub creation

Laptop currently generates a .zshrc file if one does not already exist.
However, this file is created with the # DO NOT EDIT BELOW THIS LINE
comment that does not fit with the new thoughtbot/dotfiles convention
of storing changes in .local files instead of above the placeholder
comment. If a user attempts to run laptop and then install dotfiles,
the dotfiles installation will not install .zshrc because of the
existing stub.

This change removes the creation of the .zshrc stub for both mac and
linux scripts.
check for curl in prereqs

Fixes a problem installing hub using curl
Merge pull request #115 from IanChiles/master

check for curl when installing on linux
Remove duplicate Foreman install

Heroku Toolbelt includes Foreman. Installing the gem in addition to
Toolbelt may cause future problems. For example, the Toolbelt is
auto-updating and the gem isn't. So, we might run into weird problems
with an out-of-sync foreman vs Heroku command-line tool.

Thanks, @jonmountjoy.
Fix OpenSSL::SSL::SSLError

Some users see SSL certificate errors when making API requests from
Ruby. For example:

    SSL_connect returned=1 errno=0 state=SSLv3
    read server certificate B: certificate verify failed

http://railsapps.github.io/openssl-certificate-verify-failed.html
Load Ruby 2 `gem` command before installing gems

Fixes these issues:

https://github.com/thoughtbot/laptop/issues/98
https://github.com/thoughtbot/laptop/issues/119
https://github.com/thoughtbot/laptop/issues/117
Install vim from Homebrew

Using the latest vim gets us snytax highlighting and other things that
could otherwise be different from system vim.

For example:

https://github.com/thoughtbot/dotfiles/commit/989a49d2f033077a82de43d47894cff20fcf2068#commitcomment-3740718
Componentize laptop

Refactor laptop to componentize the creation of the `linux`, 'mac` and
`linux-prerequisites` laptop files, which will allow us to share similar
tasks and configurations.  IMPORTANT: `/bin/build.sh` must be run before each
commit to re-render the laptop files. See `CONTRIBUTING.md` for details.