Fixes occasional failures of tests
Sorted `EntrySet#each` test
`Zip.sort_entries` working for zip output
Merge pull request #172 from amco/master

`Zip.sort_entries` working for zip output
Zip.unicode_names should be turned on in the unicode tests.
Add Entry#unicode_name?

This returns true if the entry has a unicode name, false otherwise.
Tidy up the unicode tests.
Set entry names encoding appropriately.

If we don't set this then we can't do things like file.exists?("Résumé.txt")
without specifically forcing it to ASCII-8BIT, which is unnecessarily clunky:

file.exists?("Résumé.txt".force_encoding("ASCII-8BIT"))

This is because entry names are always read as ASCII-8BIT even if the EFS bit is
set. This patch fixes that.

Tests added/updated to make sure that this works for both files and streams.