Meteor integration

[juliomac]

Dear Stephane Caron,

As you might know, there is a growing Meteor community out there that, I believe, could make a very good use of your package.

For it to work within Meteor applications, it is necessary to create a package. That is basically the only thing I did here. It adds only a package.js file among the ones already present
for other package managers.

All you have to do after accepting this PR would be:

1. Create an account at https://meteor.com/ (click SIGN IN, then Create account).
   After you've done that, please let me know the name of the account, and we'll add you
   as a maintainer of the organization.

2. Activate your repo on autopublish.meteor.com

   1. Head to autopublish.meteor.com, sign in with your
      GitHub account, locate this repository and enable it for autopublish by toggling the checkbox
      you'll find on the right side of the repository item. You can get an idea about how Meteor
      Autopublish works on this page, but basically
      it creates a web hook to let us know
      when you push new tags. When you'll release new versions, autopublish.meteor.com will
      automatically package the the new version of the library also for Meteor!
   2. In case you're not comfortable with autopublish.meteor.com maintaining access rights to
      your repos, please head to GitHub Application Settings
      and revoke permissions for Meteor Autopublish.

   Please note that you will not be able to toggle your repository until you have the package.js file on
   your master branch.

3. Alternatively, in case you're not willing to give read/write rights to your public repositories
   to anyone else but you (which is understandable), we will be available to provide a step-by-step
   guide to manually creating the required webhook.

Please also note that we've already published the current version of the package on
[Atmosphere]https://atmospherejs.com/juliomac/prettyphoto
(Meteor's package directory) under the name prettyphoto. If you think another
name would be a better fit, just let us know!

Thanks in advance for your availability and collaboration and congratulations on the awesome project!

Júlio Coutinho
& the Meteor Packaging Team