Allow passing DB into migration

Rakefile

   migrate
 end
 
+task 'migrate_test' do
+  require_relative './db/migrate'
+
+  migrate(db: TEST_DB)
+end
+
 task 'scrape' do
   require_relative './db/scrape'
 

db/migrate.rb

 
 require_relative 'connect'
 
-def migrate
-  db = DB
+def migrate(db: DB)
   db.create_table? :threads do
     primary_key :id
     String :title