center: true option issue

[ghost]

We are building a mobile hiking app and on a couple of trails we noticed that setting

center: true

seems to have no effect, while it works on the other trails.
For the two trails where it is not working as supposed, I think the problem is due to the fact that those trails have a cross section. This might result in a duplicated lat,lng pair in the polyline. Here is a screenshot:

[leplatrem]

Fixed by #34