Added support for IBEX index.

The system cannot know from where the ticker comes, so it will try both for each year till it gets at least one result, when that happens it will continue scanning the index which yielded some result.
Removed references to Yahoo!
Added support for caching requests.

Now all files downloaded will be stored in a static dictionary so subsequent requests will not do http requests to MEEF servers.
Fixed wrong request order between actions and IBEX index.
Close the response before attempting another requests.

Seems Yahoo! limits the number of connections.