chore(doc-gen): put typescript stuff into its own package

This means that we can now run just the d.ts file generation by running:

```bash
gulp docs/typings
```

In addition the type definition generation was messing with the other docs tasks
so separating it also fixes problems there.

docs/docs-package/readers/ngdoc.spec.js

@@ -0,0 +1,45 @@
+var ngdocFileReaderFactory = require('./ngdoc');
+var path = require('canonical-path');
+
+describe('ngdocFileReader', function() {
+
+  var fileReader;
+
+  var createFileInfo = function(file, content, basePath) {
+    return {
+      fileReader: fileReader.name,
+      filePath: file,
+      baseName: path.basename(file, path.extname(file)),
+      extension: path.extname(file).replace(/^\./, ''),
+      basePath: basePath,
+      relativePath: path.relative(basePath, file),
+      content: content
+    };
+  };
+
+
+  beforeEach(function() {
+    fileReader = ngdocFileReaderFactory();
+  });
+
+
+  describe('defaultPattern', function() {
+    it('should match .md files', function() {
+      expect(fileReader.defaultPattern.test('abc.md')).toBeTruthy();
+      expect(fileReader.defaultPattern.test('abc.js')).toBeFalsy();
+    });
+  });
+
+
+  describe('getDocs', function() {
+    it('should return an object containing info about the file and its contents', function() {
+      var fileInfo = createFileInfo('project/path/modules/someModule/foo/docs/subfolder/bar.ngdoc', 'A load of content', 'project/path');
+      expect(fileReader.getDocs(fileInfo)).toEqual([{
+        docType: 'guide',
+        content: 'A load of content',
+        startingLine: 1
+      }]);
+    });
+  });
+});
+