Expose Sass lang version via node-sass API and CLI

API Usage:

```javascript
var sass = require('node-sass')
console.log(sass.info)

/*
node-sass       3.7.0   (Wrapper)       [JavaScript]
libsass         3.3.6   (Sass Compiler) [C/C++]
Sass            3.4     (Sass Language) [Sass]
*/
```

CLI Usasge:

```sh
node-sass -v

node-sass       3.7.0   (Wrapper)       [JavaScript]
libsass         3.3.6   (Sass Compiler) [C/C++]
Sass            3.4     (Sass Language) [Sass]
```

lib/extensions.js

@@ -279,6 +279,7 @@ function getVersionInfo(binding) {
   return [
            ['node-sass', pkg.version, '(Wrapper)', '[JavaScript]'].join('\t'),
            ['libsass  ', binding.libsassVersion(), '(Sass Compiler)', '[C/C++]'].join('\t'),
+           ['Sass     ', binding.languageVersion(), '(Sass Language)', '[Sass]'].join('\t')
   ].join(eol);
 }
 

src/binding.cpp

@@ -331,12 +331,17 @@ NAN_METHOD(libsass_version) {
   info.GetReturnValue().Set(Nan::New<v8::String>(libsass_version()).ToLocalChecked());
 }
 
+NAN_METHOD(libsass_language_version) {
+  info.GetReturnValue().Set(Nan::New<v8::String>(libsass_language_version()).ToLocalChecked());
+}
+
 NAN_MODULE_INIT(RegisterModule) {
   Nan::SetMethod(target, "render", render);
   Nan::SetMethod(target, "renderSync", render_sync);
   Nan::SetMethod(target, "renderFile", render_file);
   Nan::SetMethod(target, "renderFileSync", render_file_sync);
   Nan::SetMethod(target, "libsassVersion", libsass_version);
+  Nan::SetMethod(target, "languageVersion", libsass_language_version);
   SassTypes::Factory::initExports(target);
 }