Fix for #11, Added Support for Custom Destination Names

[danyowdee]

Hi,

the script did not work for me as is because for whatever reason git svn show-externals did not separate the revision and the path in my setting.

In addition, my externals specified a customized name so this needed a little tweaking, too.

Both changes are actually contained within the first commit, but the regexp will fail for directory names that end in a non-ASCII-character. This is rectified in the second commit which uses the (non-)whitespace-character-distinction to capture the path and revision.