test input shapefile coordinate system

[erexer]

the input shapefile needs to be in a projected coordinate system in order to calculate the parameters, add a check so we can return an error message that tells the user exactly what's going wrong and how to fix it.

[erexer]

@levisweetbreu do we need to test for a specific projected coordinate system? and if so, which one?

[levisweetbreu]

@erexer I imagine it can be any projected coordinate system, I use Albers by default. The main issue is that the calculations won't work if the shapefile isn't in a projected coordinate system.