POC of using premake to compile muduo: use base, net, and simple_echo as examples

Premake is a meta build system similar to cmake, although not as mature as cmake, premake is more flexible by leveraging *lua* as its build script format, compared to cmake:
* It provides a better structured domain model: solution - project - configuration
* it is more flexible - it is easier to twist for corner cases, and extend it yourself when you need more power, write build script is also programming

Here are a few links:
* [User Guide](http://industriousone.com/premake/userguide)
* [BitBucket Repo](https://bitbucket.org/premake/premake-stable)

For this change in specific, it is obvious not a full support to use premake to build muduo, but rather a POC - which proves use premake to build muduo is feasible, and also quite elegant:)

To try with it:
1. Install [premake4.4 beta](http://industriousone.com/premake/download)
2. Run *premake gmake* to generate make file
3. Run *make -C ../build/ config=release* to build
4. See what has generated:
```
$ tree ../install
../install
├── bin
│   └── simple_echo
├── include
│   └── muduo
│       ├── base
│       │   ├── AsyncLogging.h
│       │   ├── Atomic.h
│       │   ├── BlockingQueue.h
│       │   ├── BoundedBlockingQueue.h
│       │   ├── Condition.h
│       │   ├── copyable.h
│       │   ├── CountDownLatch.h
│       │   ├── CurrentThread.h
│       │   ├── Date.h
│       │   ├── Exception.h
│       │   ├── FileUtil.h
│       │   ├── LogFile.h
│       │   ├── Logging.h
│       │   ├── LogStream.h
│       │   ├── Mutex.h
│       │   ├── ProcessInfo.h
│       │   ├── Singleton.h
│       │   ├── StringPiece.h
│       │   ├── Thread.h
│       │   ├── ThreadLocal.h
│       │   ├── ThreadLocalSingleton.h
│       │   ├── ThreadPool.h
│       │   ├── Timestamp.h
│       │   ├── TimeZone.h
│       │   └── Types.h
│       └── net
│           ├── Buffer.h
│           ├── Callbacks.h
│           ├── Channel.h
│           ├── Endian.h
│           ├── EventLoop.h
│           ├── EventLoopThread.h
│           ├── EventLoopThreadPool.h
│           ├── InetAddress.h
│           ├── TcpClient.h
│           ├── TcpConnection.h
│           ├── TcpServer.h
│           └── TimerId.h
└── lib
    ├── libmuduo_base.a
    └── libmuduo_net.a
```

If we agreed, I can work towards to port muduo to build with premake fully.

Thanks.