Throw NoSuchMethodError if the caller requests a nonexistent member

Angular--and potentially other callers--expect that when a method such
as containsKey is called on a DynamicEntity, that the object will throw
NoSuchMethodError. DynamicEntity, on the other hand, wants to ensure
that no one stashes a completion in a DynamicEntity and tries to call
it later. This patch accomodates both needs.
Get the actual symbol name via reflection

The toString method on a Symbol returns "Instance of Symbol," which is
not what was intended.
Merge pull request #25 from gsadams/nsmerror

Throw NoSuchMethodError if the caller requests a nonexistent member
Rewrite DartHtmlHttpService to not use HttpRequest.request().
Remove missed section of code.
Stray capital L in library.
Missing (.
Not using Map syntax anymore.
Add api error.
Proxy imports base not streamy.
Patch error handling in Multiplexer to not leak errors.
Return ProxyClient to throw an actual exception.
Ignore null in _handleRpcReply.
Merge pull request #27 from alxhub/proxy-http-request-fix

Fix a number of issues with Proxy in order to vastly improve error handling. We no longer leak exceptions, and the Apiary error information is available in a primitive form.