TDB2 parsing

- TDB2::load_lines was splitting the text on \n, but because the last
  line contains \n, there was an additional blank line.  This is what
  split_minimal is for.
- split_minimal contained a copy/paste bug that added the extra line
  if the input was non-trivial, instead of if the remainder was non-
  trivial.
- Fixed incorrect unit test accordingly.

src/text.cpp

@@ -143,7 +143,7 @@ void split_minimal (
     start = i + 1;
   }
 
-  if (input.length ())
+  if (start < input.length ())
     results.push_back (input.substr (start));
 }