Take renaming into account

[kumachan-mis]

see #105 and #106
There are two types of renaming:
(1) pure renaming: just renaming a PlantUML file.
(2) renaming with changes: renaming a PlantUML file, then changing it a little.

If the extension detects pure renaming(1), it should "do nothing".
If the extension detects with changes(2), it should work same as #46

Note that renaming is shown like this in GitHub:
path/to/dir/filename.puml→path/to/dir/newfilename.puml

If paths are long, it is a little tricky:
path/to/dir/verylongplantumlfilename.puml→path/to/dir/newverylongpl....
(If only one path is long, this tricky expression may not be used...?)