(Experimental) Port Envs to use conda-js

This is ready for review.

Changes:

- Uses `conda-js`. Runs conda through a subprocess
- Does not load all environments on page load
- Uses Ractive.js in some parts for templating (this is something I was experimenting with for performance reasons)
- Implements package installation, uninstallation, upgrading, downgrading; environment creation, cloning, deletion; changing settings; cleaning caches; reverting revisions
- Implements progress bars where appropriate (uses WebSockets)
- Makes "installed" tab primary one
- Can do multiple install/uninstall/upgrade
- Checks for upgrades (it does its own "new version" check for speed, but we could use `conda update --all --dry-run` instead)
- "Sticky" top bar (scrolls with page)
- Windows users are warned to close programs before proceeding

TODO:

- I think there may be some cases where the UI can get in an inconsistent state? Please let me know if you run into an instance where it didn't update the UI but should have.

Images:

![image](https://cloud.githubusercontent.com/assets/327919/3688816/1c8c7c52-133a-11e4-88d1-7ee2109e93e7.png)
![image](https://cloud.githubusercontent.com/assets/327919/3688819/221d10b4-133a-11e4-933c-bc6e41c865ea.png)
![image](https://cloud.githubusercontent.com/assets/327919/3688831/3329de96-133a-11e4-892d-a8a1e51f25e1.png)
![image](https://cloud.githubusercontent.com/assets/327919/3688833/3c55afcc-133a-11e4-8a49-c4c878b32be9.png)