Handle exception caused by gpxpy library.

+ See https://github.com/tkrajina/gpxpy/issues/10.
Fix typos in comments.
Merge pull request #6 from johnjohndoe/bugfix/gpsexception-on-broken-files

Handle exception caused by gpxpy library.
Merge pull request #7 from johnjohndoe/fix-typos

Fix typos in comments.
Enable reading folders recursively.
Merge pull request #8 from johnjohndoe/feature/read-folders-recursively

Enable reading folders recursively.