Util.parse_files/2 trips on directories

[maco]

Bug Description

19:37:55.993 [error] Task #PID<0.190.0> started from #PID<0.94.0> terminating
** (File.Error) could not read file "lib/MyApp": illegal operation on a directory
    (elixir 1.18.3) lib/file.ex:385: File.read!/1
    (meandro 0.1.0) lib/meandro/util.ex:33: Meandro.Util.file_to_ast/1
    (elixir 1.18.3) lib/task/supervised.ex:101: Task.Supervised.invoke_mfa/2
    (elixir 1.18.3) lib/task/supervised.ex:36: Task.Supervised.reply/4
Function: #Function<5.110493450/0 in Meandro.Util.parse_files/2>
    Args: []

To Reproduce

Add Meandro to a Phoenix app and run mix meandro --files=lib/*

Expected Behavior