Add a * when importing from a directory full of parquet files

[dsmilkov]

Feedback from Sean:

I’m importing a dir full of parquet files, and I pass the path of the dir containing all those files, I get a “no files matching” error. If I add *.parquet on the end, it works fine. I’d propose perhaps doing that automatically if passed a dir ending in “/” as it’s pretty common to have a folder full of parquet files (and maybe likewise for other formats). Totally trivial, just took me a second to work out