defined the has and belongs to many association between the event and category model
created the category table and join table between categories and events
created 7 seed categories
moved the add event button on the index page to the top
created categories controller
added checkboxes when creating a new event and creates a new row in the join table based on what is selected
can now store multiple categories per event
category names are now clickable
deleted unnecessary code to make the names clickable
fixed merge conflicts in schema, index html and routes