Fix `precision` option default value

Sass v3.2 or later outputs decimal numbers with 5 digits after point.

See also: https://github.com/sass/sass/commit/edc2634ba08881ceec5aa1835f9e0284e781ffa9
Merge pull request #146 from hail2u/precision-option-default-value

Fix `precision` option default value
Fix and improve syntax checking (`check` option)
Merge pull request #147 from radkodinev/skip-creating-when-checking

Fix and improve syntax checking (`check` option)
minor tweaks
changelog
0.8.1
dependent-files merge with upstream/master