Check SqlComposition ending and remaining.fragment

[soulstompp]

parse() doesn't return remaining like parse_template did. Does it check internally that any remaining.fragment is empty?

Originally posted by @spazm in #14

We should ensure that we have parsed everything we could with nothing remaining and we should make sure that everything after a Sql::SqlEnding in a SqlComposition is nothing but whitespace. Anything besides whitespace could be someone pulling a fast one.

Rather than checking any lingering Sql::SqlLiteral objects, I'd prefer that the parser distinguish the literal from Sql::Whitespacing blocks. The Sql::Whitespacing should be used for contigous whitespace but shouldn't break up the continuation of an already existing Sql::SqlLiteral.