Ability to interpolate HTML inside text blocks

[darthdeus]

Currently

p
  | Hello #{link "world", to: "/foo"}

will result in an error

protocol String.Chars not implemented for {:safe, [60, "a", [[32, "href", 61, 34, "/world", 34]], 62, "Hello", 60, 47, "a", 62]}

[doomspork]

Thanks @darthdeus! Want to take a shot at implementing this?

[Rakoth]

@darthdeus could you confirm it is fixed with current master?

[Rakoth]

fixed by #130