Without any file modifications, `harmonic build` should always generate the same output files

[UltCombo]

Cross-platform

• Add timezone setting #84 - Add timezone setting.
• Normalize directory separator in the generated harmonic.js's getPosts() and getPaths()'s file property #146 - Normalize directory separator in the generated harmonic.js's getPosts() and getPaths()'s file property.

Other

• Should not overwrite the existing RSS feed if nothing changed #147 - Should not overwrite the existing RSS feed if nothing changed.

[UltCombo]

Although these issues are mostly minor things, the diff is really annoying when deploying the same site on different platforms.