Issue with Examples

I am having issues running the examples locally on a mac.

https://github.com/lob/lob-python/blob/master/examples/create_postcards_from_csv/create_postcards_from_csv.py#L16

I had to change files be opened like this:

"open('postcard_front.html', 'r')"

instead of 

"s.path.dirname(**file**) + '/postcard_front.html'"

to get it to work.
