make checkVersions consider build version

Currently, the build version is extracted by the regex (by `parseVersion`) but not used in the version check.

See this discussion.
https://groups.google.com/d/topic/tiddlywikidev/-WgmkTyeIM0/discussion

The patch solves this.

I tested the patch dragging my plugin 0.6.0+75 to a wiki with plugin version 0.6.0+74 and vice versa.

Regards
Felix