Merge pull request #7 from yohanboniface/fix_feature_property

Fix "maximum recursion depth exceeded" in Feature.properties (+ PEP8)
Merge pull request #8 from yohanboniface/csv_decode

First version of a CSV decoder
[GPX.decode] Do not fail if some field is empty
Merge branch 'gpx_empty_field' into leafletstorage

Conflicts:
	tests/gpx.py