Make partial names support additional special characters and quote escaping

...scaped aspects.

Copying test from https://github.com/wycats/handlebars.js/blob/2a4819d75cba7513946af5cf28ee22881561814f/spec/partials.js#L144
This is also motivated by wanting to have file-named partials with / and .s e.g. foo/bar.html