Create Map on Leaflet

[elhagen13]

We will be logging the locations of trees that we record, and we would like all the trees to be shown on an interactive map. For now, we just want to make sure the library works with our project.

• Use Leaflet and create a basic map that displays on our website
• Add a few markers for trees in dummy locations

Later, our trees' locations will be stored in the database, which will update what appears on the map. Look into how to do this for now, and write about it in your PR!