Merge pull request #37 from zozlak/master

A bunch of enhancements for dealing with large tar archives

Merge branch 'pr/26' into yield

* pr/26:
  Whoops, fixed wrong variable name.
  Added yieldContents() to keep contents() backward compatibility.
  Use yield in contents() instead of returning a single array with all results.

moved constant definition to top

additional zero file testing

Existing tests didn't 100% make sure a zero byte file was correctly
added and extracted. It was. Now we also have the tests to prove it.

renamed FileInfo::match() to FileInfo::matchExpression()

In PHP8, `match` is a reserved keyword. In preparation this renames the
method. A fallback via __call() is provided which will trigger a
E_USER_NOTICE.

supress chmod and touch warnings

On some file systems these commands will fail. It's unclear what systems
those are, I can reproduce it for touch() on my android phone (but not
on my tablet).

Instead of littering the output with potentially thousands of warnings
we supress them here. Ideally we should probably do something with them,
but I don't know what.

Maybe a strict setting that turns them into exceptions, would work? PRs
welcome.

extracted exceptions into their own files

required for PSR-2

check for broken iconv setup

use trusty for running tests on travis

Throw an exception when a file changes during reading

see discussion at #17