start v0.4.0 dev, kind-of

+ Now has icon in browser for ease of use
+ Now requires "tabs" permission
~ Manifest/options page updated to display v0.4.0
add JS for navigation via popup to injector.io
adds syntax highlighting via CodeMirror (implements #12)
minify CodeMirror files (did not notice how large they were)
replace mentions of $("#si_cssRulesBox") in option.js with CodeMirror's editor object
replace alert() calls with custom notifications.
Merge pull request #15 from McSherry/v0.4.0-dev

v0.4.0 complete