Add zipinfo() and zipok()

* and relevant tests
Use read.table for zipinfo and give cols sensible classes
zipinfo(): Cope with files with spaces 

* and add test for that
* and one file archive
Prepare v0.2 release
Deprecate file.hardlink in favour of base::file.link
Update README.md with CRAN release in mind
typo in README
Prepare v0.3 release for CRAN