Re-enabled auto-detection of zipfile, also with different object filename

It now automatically handles:
- xl/vbaProject.bin (MS Excel);
- word/vbaProject.bin (MS Word).
added MIT license
Merge pull request #6 from certego/feature/zipfile

ZipFile auto-detection
zipfile.is_zipfile identifies OLE doc as zipfile
fixed incorrect value check in PROJECTHELPFILEPATH Record
extract VBA macros: fixed infinite loop when output file already exists
improved logging output, set default level to INFO
Merge pull request #7 from decalage2/master

Fixed a couple bugs in the VBA macros extraction code