use istanbul for code coverage

* Requires no instrumentation
* add `make test-cov` to generate coverage reports
issue 83 IE9/10: returned if this.xhr was undefined
Merge pull request #132 from asdfryan/master

Issue 83 fix: IE9/10 error
added query.eio to take protocol version from parser. Also changed Socket.protocol to take that same protocol version
capitalized eio, added a comment saying that the protocol is an int, not a string
Merge pull request #133 from asdfryan/eioversion

Issue 65 fix: Added eio query string
require 'emitter' versus 'emitter-component'

Use the github style dependency to just grab the emitter package from
github. Use the long form because short form is all sorts of broken with
npm.
Merge pull request #131 from shtylman/emitter

require 'emitter' versus 'emitter-component'
Merge pull request #130 from shtylman/coverage

use istanbul for code coverage
use bundleable version of ws
use "browser" field to shim "xmlhttprequest" module

When packaging for client side use, use the local browser shim for
xmlhttprequest