Provide a top-level transformation hook

[calvinwiebe]

This adds in a simple hook to be able to get the transformed source without it being immediately written to disk. I did this as I wanted to use streamline with gulp, in a plugin here. I realize that most of the individual transform functions for the different runtimes are exposed. However, there is a lot of useful option parsing and also plain .coffee compiling provided in compile._js.

Details:

1. Added a noWrite option.
2. Factored out some common code to be used by both exports.compile and exports.transform
3. I ran build.sh to generate a new ./lib/callbacks/compile.js. I hope that was appropriate.

[bjouhier]

@calvinwiebe Thanks. I'm on vacation. I'll review in 10 days because this is difficult with just a phone.

[bjouhier]

It looks good but you have removed the trailing spaces at the end of documentation lines (prefixed by /// - note: the space after the 3 slashes is important too). These comments are used to generate markdown files and trailing comments are meaningful in markdown.

Can you restore these lines and resubmit the PR. Thanks in advance.

[calvinwiebe]

Will do! I'll close and resubmit.