* The `thread`-gem is required for the script, because otherwise Ruby throws an error that `Queue` in line 259 is an uninitialized constant
* The variable `p` was previously in the same method with the status message saying `OK ‹path› ‹converted scopes›`. But `p` is now defined in load_grammars() and thus not visible when showing the OK-message in install_grammars(). This was solved by adding a path-parameter to install_grammars().
convert-grammars now supports a few flags that we can use to make it
dump out the YAML just for the local grammar submodules. We can then
compare this to the YAML that's actually in grammars.yml to check that
they're the same. If they aren't, grammars.yml needs to be updated.
This will help catch mistakes like using the wrong scope name.
