cmp_version - Compare version1 and version2.
Returns cmp-style (C-style), i.e. < 0 if lefthand (version1) is less, 0 if equal, > 0 if righthand (version2) is greater.
@param version1 <str> - String of a version
@param version2 <str> - String of a version
@return <int> -
-1 if version1 is < version2
0 if version1 is = version2
1 if version1 is > version2