Minor improvements

- Fix whitespace issues
- SlimAssets::$assets is no longer a static variable
- Fix variable name typo in SlimAssets::ensureFileExists
Use non-www version of cssminifier.com
Improvements to how compacted assets are managed
Stop updating the last modified time of compact files
Fix asset generation in distributed environments
Fix typo
"compileLess" does not write to original files
Merge pull request #1 from erikwiffin/master

Failed strict error checking.