sanitizeRegex chopping dots

~~~ go
var sanitizeRegexp = regexp.MustCompile("[^a-zA-Z0-9/_-]")
~~~

The above, as part of RenderIndexes with rss.xml template, results in Permalink being set to ".../indexxml" instead of ".../index.xml".

If I change it to 

~~~ go
var sanitizeRegexp = regexp.MustCompile("[^.a-zA-Z0-9/_-]")
~~~

It works ok.