turicreate.load_audio broken with home directory present.

[hoytak]

The following code generates a dataset that has no entries:

In [13]: import turicreate as tc
    ...:
    ...: data = tc.load_audio("~/data/ESC-50/audio/")

However, the same code where the ~ is replaced by the absolute path name works fine.

[TobyRoseman]

A ~ in the path also doesn't work with tc.load_images. It does however work for tc.load_sarray and tc.load_sframe.

[TobyRoseman]

A ~ also works in the path for tc.load_model and tc.load_sgraph. So this just needs to be fixed in tc.load_audio and tc.load_images.

The functions that do this properly all seem to use the _make_internal_url method. It seems like using this will also fix other issues too (e.x. S3 paths).