Fixed dialyzer errors

```
  make dialyzer
    Checking whether the PLT is up-to-date... yes
    Proceeding with analysis... done in 0m1.27s
  done (passed successfully)
```

And also fixed some styling issues
Line 76 is too long: "-spec handle_call(Request :: term(), From :: {pid(), Tag :: term()}, State :: #state{}) ->".