update env.example

Update `env.example` file to include `DB_CONNECTION` settings, since the default is `pgsql`. 

Closes #19

Author: profnandaa

.env.example

@@ -6,6 +6,7 @@ DB_HOST=127.0.0.1
 DB_DATABASE=hackathon
 DB_USERNAME=homestead
 DB_PASSWORD=secret
+DB_CONNECTION=<mysql, pgsql, etc>
 
 CACHE_DRIVER=file
 SESSION_DRIVER=file