v1.8.0

• Add tests for everything (#121)!
• Use valid license for npm (af6243b).
• Instantiate the in-memory filesystem only once, meaning it can be shared when using multiple middleware instances with one webpack config (#120).
• When sending requests with a Range header, the status code would not always be correct (cedc09f).
• Middleware would not work with a proxy (#80).
• Add index option (default: index.html) to customize the file used as index for a directory (#123).