Ignore empty info in diff line

Fix bug where colons in paths raise a `ValueError` on `diff()` calls.

This commit introduces a potential fix for #1490 and #1483, in which an
`invalid literal for int() with base 10: 'n'` exception was raised
within a diff operation. Within `_handle_diff_line()`, we split the
output of `git diff-tree` on colons (`:` characters), under the
assumption that there are no colons within the paths of the files being
diffed. On POSIX systems this is not a valid assumption. The fix is to
split on `\x00:`, since a null character always precedes the colons we
actually need to split on.

A test already existed for this case (`test_diff_file_with_colon()`),
but it was marked as skipped.

* Split on `\x00:` instead of `:` in `_handle_diff_line()`.
* Unskip `test_diff_file_with_colon()`.

feat(blame): Support custom `rev_opts` for blame

The `git blame` CLI offers a repeated `-C` option that can be used to detect
lines that move within/between files. While a slower operation, it yields more
accurate authorship reports.
https://git-scm.com/docs/git-blame#Documentation/git-blame.txt--Cltnumgt

While GitPython does enable passing custom kwargs to the command line `git`
invocation, the fact that kwargs is a dictionary (i.e. no duplicate keys) means
that there was no way to request the `-C` option in `git blame` more than once.

This commit adds an optional `rev_opts` parameter to the `blame` method which
accepts a list of strings to propagate to the CLI invocation of `git blame`. By
using a `List[str]` for `rev_opts`, users of GitPython can pass now the `-C`
option multiple times to get more detailed authorship reports from `git blame`.