support both HTML (with) and XML (without HTML specific behaviour)

* new options '--xml' and '--html' (default) added
* XmlDialect added without shortcuts, fill attributes and so on
* Vim: ftplugin 'xml' added as symlink
* Vim: call sparkup.py with the filetype as argument
* so my XML can have <area> tags without attribute filling
* yet my HTML still can
Merge branch 'tqmz/master'