run! method should respect --no* flag passed to svn2git

This provides a workaround for the problem described in #106.

Basically it just makes sure `fix_trunk`, `fix_branches`, and `fix_tags` are not called in the `run!` method if `--notrunk`,  `--nobranches`,  or `--notags` respectively are passed to the svn2git command.

As of right now, the --no* flags only appear to affect the initial git clone, not later rebases.