Fix task sequence for docs:typescript

Author: lehni

gulp/tasks/docs.js

@@ -50,7 +50,7 @@ Object.keys(docOptions).forEach(function(name) {
 
 // The goal of the typescript task is to automatically generate a type
 // definition for the library.
-gulp.task('docs:typescript', function(callback) {
+gulp.task('docs:typescript', ['build:full'], function(callback) {
     run(
         'docs:typescript:clean:before',
         'docs:typescript:build',