Update licenses for 53 casks

A few notes:

- `tau` listed as `:oss` - Custom license, appears to be based on/similar to the MIT license
- `matplotlib` listed as `:oss` - Uses only BSD-compatible code, exact license is based on the Python Software Foundation license, see http://matplotlib.org/users/license.html
- `google-chrome` listed as `:gratis` - http://www.google.com/intl/en/chrome/browser/privacy/eula_text.html  To quote en.Wiki

>Chrome's WebKit & Blink layout engines and its V8 JavaScript engine are each free and open-source software, while its other components are each either open-source or proprietary. However, section 9 of Google Chrome's Terms of Service designates the whole package - Chrome itself - as proprietary freeware.

- `snes9x` listed as `:other` - Source is available, but not 'open' for the purposes of reusing.  snes9x is gratis for non-commercial purposes.  See the source for the full license but the relevant info:

>Snes9x is freeware for PERSONAL USE only. Commercial users should
>seek permission of the copyright holders first. Commercial use includes
>charging money for Snes9x or software derived from Snes9x.

- `chocolat` listed as `:commercial` - This could theoretically be billed as ':freemium' but after the trial period is over the app apparently forces you to use Comic Sans (http://gizmodo.com/5909063/how-to-make-sure-someone-will-buy-your-app).  Some may consider paying to avoid that a freemium, but I and many other would argue a Comic Sans-only texteditor is no texteditor at all.