Point to ruby 1.8 shim

Using a shim allows us to catch when 1.8 of ruby is not present and provide other options.

#ignore
Do not try to show non-existing PDF when using TextMate as viewer

Typesetting a TeX file can fail without our tex output parser picking up any errors/warnings, in this case there will be no PDF file but we would previously still redirect the HTML output view to show the (non-existing) PDF.
Merge textmate master