Simple patch which just uses 1.5.1 instead of 1.3.3 for the version

This is branched from the `lesscss-1.3.3` tag - which means that it contains none of the extra resource/parsing fixes that have come since 1.3.3 (which seem to have destabilized the plugin).

Using this patch alone, it is possible to use less version 1.5.1 by setting a dependency on the lesscss-maven-plugin.