Upgrade to BrowserFS v0.3.1

[jvilk]

BrowserFS v0.3.1 brings with it zip file support, proper error codes, less overhead, and some compatibility-breaking changes. Actually, I think it brings with it the new Dropbox and HTML5FS file systems, too.

Namely, we no longer define BrowserFS.node.

With this upgrade, I plan to:

• Configure RequireJS so that it understands how to serve the fs and path modules appropriately, and define process as a variable within the library scope so classes can treat it as a global. This will enable TypeScript to appropriately typecheck our calls into these modules using the Node typings.
• Fix hacks where we use the node variable to detemine if we are in the browser to use process.platform.
• Fix hacks around the lack of error codes in older versions of BrowserFS.

[jvilk]

It looks like I'm going to need to define RequireJS shim module files for fs and path, as it requires that each module be defined in a separate file. Then, I can alias fs and path to these files.

It's not clear how I can do the same for process without simply making it a global variable in a development build and a scope variable in a release build.

For Buffer, I can either take the same route as process, or change our code to use require('Buffer').

[jvilk]

Just a side note from the commit message:

• [ ] The FileOps test fails in the browser; there might be a BFS regression.
• [x] Builds assume that process and Buffer are globals. This is acceptable atm for the dev build, but unacceptable for the release build. I will fix this when I almond-ize doppio.js and force it to expose functionality through a single global.

[jvilk]

I gave up on chmod support, as it's irrelevant in the browser. So this is good now.