Hazel ignore numbers at the end of new project names

[dombarnes]

Steps:

1. run hazel demo
2. run hazel demo2

Expected:
Two folders created with app structure, called demo and demo2

Actual:
Running second command shows that all files already exist and only folder demo is created.

[peterhellberg]

This is working as intended:

hazel/lib/extensions/string.rb

Lines 18 to 20 in 51de275

	def directory_name
	self.downcase.gsub(/[^a-z|\-|\_]/, '')
	end