add missing spaces into function declarations

There is no consistency in putting space before parentheses in anonymous function declaration.
For example in [README.MD](https://github.com/gulpjs/gulp/blob/master/README.md#sample-gulpfile) Sample gulpfile:
At line 23 there is no space before ()
```javascript
gulp.task('images', function() {
```
At line 31 there is a space
```javascript
gulp.task('watch', function () {
```

I've added missing spaces according to [code conventions](http://javascript.crockford.com/code.html)
There were also some missing spaces between ')' and '{'. I've added them too.