add Chinese translation document

The pull request contains the Chinese translation for "Guide and Overviews (Core)" part. 

The translation covers the doc in http://docs.scala-lang.org/overviews/ , except Reflection & Macros

We used transifex as our working platform, the address is https://www.transifex.com/projects/p/12345-1/

The translated doc list:

- The Scala Actors Migration Guide
- Value Classes and Universal Traits
- String Interpolation
- Implicit Classes
- Futures and Promises
- Scala’s Parallel Collections Library
- The Architecture of Scala Collections
- The Scala Actors API
- Scala’s Collections Library