remove sightings_species table from database
make spec pass for association between species and sightings.
create validation for presence of date, longitude, latitude, and species_id for a sighting.
remove 'new' method and html file.  Relocated 'new' form to show up on 'index' html file.
make 'create' method to add a sighting to a species.  Make 'index' method to list all sightings.
create 'index' method to list sightings, 'destroy' method to delete sightings, and 'edit' method to edit sightings.
create 'update' method to make 'edit' method work.
create regions table.  Add region_id to sightings table.
create association between regions and sightings.
validate presence of region name when adding to regions table
make 'create' method for regions for user to add a region; create a dropdown menu for a region to be added to sightings.