Explain what happens if --verbose flag is set

There is no output that explains what is going on when the program is
running . Add a flag called --verbose, and print what happens to the
console if it's set.

Signed-off-by: Marcus Karlsson <mk@acc.umu.se>
Show error message if clone fails

Catch any error generated while cloning a repository and show the user
that the operation failed.

Signed-off-by: Marcus Karlsson <mk@acc.umu.se>