only a shallow copy of given `options` to avoid clone-of-prototype surprises.

This is for create*Client, <server>.{get|put|...}, etc. APIs.

Commit f49e2c2 introduced potential cloning of given `options.log`
Bunyan Logger objects in the `create{Json,String,Http}Client()` APIs.
This would result in an abort on the first log write:

    Assertion failed: (args.Holder()->InternalFieldCount() > 0), function WriteStringImpl, file ../src/stream_wrap.cc, line 298.
        Abort trap
Merge pull request #316 from trentm/shallow-clone

only a shallow copy of given `options` to avoid clone-of-prototype surprises