Switched engines.node semver operator

Avoids warnings from Heroku:

PRO TIP: Avoid using semver ranges starting with '>' in engines.node
See https://devcenter.heroku.com/articles/nodejs-support
See https://github.com/isaacs/node-semver#ranges
Merge remote-tracking branch 'rmm5t/node-semver'

Conflicts:
	package.json
Merge remote-tracking branch 'public/master'
require a content-type header
Merge pull request #22 from github/require-content-types

Require a content-type header
whitelisted image mime-types
ensure image types are explicitly checked
re-render the js
don't log the contentType
tests for image,text/html content types
disable svg+xml proxying until a better solution appears
Merge pull request #24 from github/strict-content-type-checking

Strict content type checking
handle empty content-types again
Merge pull request #26 from github/empty-content-type-again

Handle empty content-types again
Revert "disable svg+xml proxying until a better solution appears"

This reverts commit 60689db9233d04910cadedf137a3b6ea7ed04d45.
cover people who take on the utf-8 charset too
Merge pull request #27 from github/enable-svg-again

Enable SVG again
match accepted content types on prefixes before the ;

http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.17
doh
doh, forgot the rendered js