Language Specification in Markdown format

Fixes #213.

This pull request adds the language specification in Markdown format.

The pull request also includes a tool (word2md) that can convert Word documents to Markdown format. The tool uses the Word Automation APIs to start an instance of Word and access the contents of the document being converted. The tool must be run using the cscript.exe script host and requires Word to be installed on the target machine. The tool recognizes the specific Word styles used in the TypeScript Language Specification but could easily be adapted to other uses.

Note that the specification is tagged such that you can reference sections by their section number in hyperlinks. For example:

https://github.com/Microsoft/TypeScript/blob/specInMarkdown/doc/spec.md#3.6.1
task generate-diagnostics should be a lot like this work. you will need to first compile scripts\word2md.ts, then run.

here is a sample.. I did not try to run it though :)

```JavaScript
var docDirectory = "doc/";

var word2MDJS = path.join(scriptsDirectory, "word2md.js");
var word2MDTS = path.join(scriptsDirectory, "word2md.ts");
var specWord = path.join(docDirectory, "TypeScript Language Specification.docx");
var specMD = path.join(docDirectory, "spec.ms");

file(processDiagnosticMessagesTs)

// processDiagnosticMessages script
compileFile(word2MDJS,
            [word2MDTS],
            [word2MDJS],
            [],
            false);

// The generated diagnostics map; built for the compiler and for the 'generate-diagnostics' task
file(specMD, [word2MDJS, specWord], function () {
    var cmd = "node " + word2MDJS + " "  + specWord;
    console.log(cmd);
    var ex = jake.createExec([cmd]);
    // Add listeners for output and error
    ex.addListener("stdout", function(output) {
        process.stdout.write(output);
    });
    ex.addListener("stderr", function(error) {
        process.stderr.write(error);
    });
    ex.addListener("cmdEnd", function() {
        complete();
    });
    ex.run();    
}, {async: true})


desc("Generates a markdown version of the language specificiation");
task("generate-spec", [specMD])
```