smokestack.capture()

Enables screenshotting of the current tab!

Still quite dirty, in need of documentation and tests.
tap-spec test output
Don't prune dependencies

This causes some quirks with bundledDependencies in some versions
of npm.
documentation for chrome extension
remove --tape

Better to just add a test at the end to shut down the window
timeout for window.close
update tape example
beginning firefox support

currently blocked by issues with window.close(), fixable
fix most firefox issues
test both chrome and firefox
make chrome the default again
expose port to CLI
remove proof.js
capture example
capture: error when not on chrome (for now)
handle errors properly in firefox
Preliminary Saucelabs support

Cleanup required, but functional. No tests yet.
Try it out using:

```
browserify some/test.js | DEBUG=smokestack smokestack -b saucelabs
```

Note that you'll also need:
* process.env.SAUCE_USERNAME
* process.env.SAUCE_ACCESS_KEY

/cc @timoxley
tests for saucelabs
update README.md
proper API/CLI support for sauce