Add new / updated file functions

[oubiwann]

Needed:

• [x] expand-home-dir
• [x] home-dir
• [x] user (maybe belongs in another module)
• [x] read

As for that last one, we need a wrapper that always expands dirs and returns appropriate error messages, etc.

Blocking:

• https://github.com/lfex/lxml/issues/14

[oubiwann]

Done.