mixing of concerns in readFile

[eliasmalik]

https://github.com/FAC10/week4-jajascript/blob/master/src/handler.js#L10

The readFile function sounds like it should generic function for reading a file, but in fact it is half-way between that and a handler; it understands the res interface as well as knowing that handler.notFound exists. The logic for how to respond to the client should typically live explicitly in the handler, unless there is significant complexity that you are trying to manage.