Fixed nbdiff running outside diff tree
added custom exception, fixed nbdiff running only from root
changed relative paths to absolute
small changes
Merge branch 'master' into outside_git_dir_exception
fixed tests
all tests fixed
syntax corrected
changed version
Merge pull request #227 from bpipev/outside_git_dir_exception

Fixed nbdiff running outside git tree
Update setup.py

Updated for version 1.04