fix build on windows

Author: blagoev

gulpfile.js

@@ -1,8 +1,10 @@
-var gulp  = require('gulp')
-var shell = require('gulp-shell')
+var path  = require('path');
+var gulp  = require('gulp');
+var shell = require('gulp-shell');
 
+var taskPath = path.resolve('./node_modules/.bin/tsc');
 // build
-gulp.task('build', shell.task([ './node_modules/.bin/tsc' ]));
+gulp.task('build', shell.task([ taskPath ]));
 
 // default
 gulp.task('default', ['build']);