Engine init looks up current Sass number precision

Sass defaults to 5 digits of precision when performing calculations. This clashes with popular css frameworks like Bootstrap and Foundation. There is ongoing, unresolved discussion as to what defaults to uphold sass/sass#1122.

In the meantime, libsass has made this configurable, but defaults to Sass' values, i.e. sass/libsass#287 and sass/libsass#675

Common workarounds involve editing the precision value directly, i.e. https://github.com/twbs/bootstrap-sass/blame/master/README.md#L78 using the provided accessor http://sass-lang.com/documentation/Sass/Script/Value/Number.html#precision%3D-class_method

This commit simply makes sassc-rails pass along that default value from Sass proper.

lib/sassc/rails/template.rb

@@ -21,6 +21,7 @@ def call(input)
           syntax: self.class.syntax,
           load_paths: input[:environment].paths,
           importer: SassC::Rails::Importer,
+          precision: ::Sass::Script::Value::Number.precision,
           sprockets: {
             context: context,
             environment: input[:environment],
@@ -52,6 +53,7 @@ def evaluate(context, locals, &block)
           syntax: syntax,
           load_paths: context.environment.paths,
           importer: SassC::Rails::Importer,
+          precision: ::Sass::Script::Value::Number.precision,
           sprockets: {
             context: context,
             environment: context.environment