Import index file in path without recurse

[OsirisFrik]

Added flag and logic to import index file in path without recurse flag

Sometimes can use a folder to group a modules and keep clean files structures, we can't import a index file (if exists) from the path without recurse flag.

./
 ┣ modules
 ┃ ┣ b.js
 ┃ ┣ c.js
 ┃ ┗ index.js
 ┣ a.js
 ┗ app.js

requireDir('./', { indexFile: true })

// Return
{
  a: require('./a.js'),
  modules: require('./modules')
}