Updated test scenarios to reflect optional and substitute ingredients
Created substitutions table.
Substitute ingredient associations functioning and added properly from seeder CSV.
Recipe search model updated to support substitutions.
Added 'optional' boolean column to ingredients table.
Optional boolean assigned to CSV seed data. Handles for nil & empty values.
Search ignores optional ingredients
Deleted erroneous '}' in application.css that was causing tests to fail.
Merge pull request #9 from davidguerette/ingredient_substitutions

Ingredient substitutions