Update to version 19.4 of windshaft

... to resolve "npm install" issues. There's a version 20.0, but 19.4 seems a safer bet.
Merge pull request #41 from RickMohr/update-windshaft

Update to version 19.4 of windshaft
Make debugging easier by not forking when in debug mode
Convert boolean values to SQL literal TRUE or FALSE
Merge pull request #42 from maurizi/fix/boolean-queries

Fix queries using boolean literals
Merge pull request #43 from maurizi/fix/boolean-queries

Fix queries using boolean literals
Merge pull request #44 from OpenTreeMap/release

Merge pull request #43 from maurizi/fix/boolean-queries