Fix quadratic dict:append/3 behaviour and use more idiomatic Erlang.

[pichi]

dict:append/3 appends value at the end of the list which has quadratic behaviour. As stated in documentation:

For example append/3 could be defined as:

append(Key, Val, D) ->
    update(Key, fun (Old) -> Old ++ [Val] end, [Val], D).

The solution is to prepend value in front of list using dict:update/4.

This version is about 24 times faster than using dict:append/3 for given data on mine computer.