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`.

That way people who use it won't be deterred, while it unifies style
everywhere.

This commit adds the `strip_newline` flag to the `Git.execute` method.
When this flag is set to `True`, it will trim the trailing `\n`. The
default value is `True` for backward compatibility. Setting it to
`False` is helpful for, e.g., the `git show` output, especially with the binary
file, as the missing `\n` may invalidate the file.