[Bugfix] Explicitly requiring base_bot

Base bot should be included before any other bot as it now throws this exception : 
```
/home/mohamedbassem/repos/vindinium-starter-ruby/bots/random_bot.rb:1:in `<top (required)>': uninitialized constant BaseBot (NameError)
	from /home/mohamedbassem/repos/vindinium-starter-ruby/env.rb:19:in `require'
	from /home/mohamedbassem/repos/vindinium-starter-ruby/env.rb:19:in `block (2 levels) in <top (required)>'
	from /home/mohamedbassem/repos/vindinium-starter-ruby/env.rb:18:in `each'
	from /home/mohamedbassem/repos/vindinium-starter-ruby/env.rb:18:in `block in <top (required)>'
	from /home/mohamedbassem/repos/vindinium-starter-ruby/env.rb:17:in `each'
	from /home/mohamedbassem/repos/vindinium-starter-ruby/env.rb:17:in `<top (required)>'
	from client.rb:1:in `require'
	from client.rb:1:in `<main>'
```