Eliminate overloads of CharStreams.fromString()

[BurtHarris]

The typescript handbooks says: Don’t write several overloads that differ only in trailing parameters.

added test case for source name

[BurtHarris]

@sharwell, this 4.7 change around factory methods on class CharStreams is cool. With that interface, I'm pretty sure we can implement CharStreams.fromFileName(), at least on node.js, because one of the few synchronous I/O operation supported is reading a whole file.

I'll see how that goes, and add it to this PR if appropriate.

[BurtHarris]

@sharwell that was weird, the appveyor job ran tslint, and barfed on my lack of trailing commas is lists.

When I ran npm install, it didn't catch the commas. Seems like if we run tslint on appveyer, we should run it before commits too.

[BurtHarris]

Related #163, this really calls for a full codebase review.