Support "<" in the templating language (#499)
Support "<" in the templating language (#499)

The templating language used for code generation uses `<` and `>` as its
delimiters.  This results in syntax errors when trying to use the beginning
delimiter as an actual character, not as invoking a template.  Add an explicit
command (`<lessthan>`) to inject `<` as needed.
thriftrw/thriftrw-go,thriftrw/thriftrw-go,thriftrw/thriftrw-go