Corrected the --line_mappings so it truly limits the "Connected To" table by the given --line, instead of providing the list of all stations connected regardless of the requested line. There were cases before when a station being connected to its neighbour only on one line (see new line-restricted syntax by Map::Tube) appeared to be connected along all lines it had been assigned to. prepareline_mappings() is now sending the line name to Map::Tube::get_linked_stations() which has started considering such restrictions since Map::Tube v5.1.0.
Upgraded dependency on Map::Tube v5.1.0.
Switched to dotted-decimal versioning (v-strings).