A small update to satisfy a request of a spigot user named MrEngMan.
MrEngMan had requested the addition of banners and signs to the list of materials that do not obstruct elevator teleportation.
I can say that I (sorta) did that.

The previous method of detecting whether the block obstructs teleportation was through Bukkits own 'Material .isSolid()' method. Unfortunately this did not include signs and banners. In this newer version, a text file named "nonobstructiveMaterials" is generated in the Elevators plugin folder on first run. This will contain a list of blocks that will not obstruct an elevators usage. (The default list is the same results as what the Bukkit method would return, but I did go ahead and include banners and signs out of the box).

To add a block to the list, simply add a new line and enter in the name of the block as shown at: https://hub.spigotmc.org/javadocs/spigot/org/bukkit/Material.html