5.1.0

• Added: files with the same content will only be imported once. Previously, only the full path was used to determine if a file has already been imported in a given scope.
  Now, we also test create a hash with the content of the file to check if a file with the same content has not already been imported.
  This might be usefull if some modules you import are importing the same library from different places (eg: normalize might be as dep for several modules located in different places in node_modules)
  (#29)