Adding History-related grunt tasks

This is a set of history related tasks that Dav asked to be added to grunt-yui-contrib.

history-rollup, Creates History Rollup file (Run before history-replace)
history-populate, Populates History files with @VERSION@ if not there already 
(actually adds the whole entry e.g.
```
@VERSION@
------

* No changes.
```
)

history-replace, Replaces @VERSION@ in History files with *release-version*