Now reads two file names from an archive.
Refactors File and File::Header
Adds some documentation

Gemfile includes a modern version of rdoc, so on a Mac you can say

  bundle exec rake rdoc
  open doc/index.html

and view the docs.

Adds a rake task.

Adds Stuart Watt to the readme.
Refactors some header processing.

This moves some code out of Archive::TarStream into
Archive::TarStream::File::Header where it belongs.
Add rake task for running flog

This also adds instructions for finding rake tasks in the README.md
Removes pre-cooked tarfiles.

It seems sensible to me to generate the test tar file from raw files
using rake, so this removes test1.tar from the repository and lets
us create it when needed.
Moves rake tasks out of lib.

This stops flog seeing then, and their being included in the documentation.
Adds better testing for Archive::TarStream::File::Header
Minor clean-ups for pull-review.
Properly handles file names ending in a space.
Does more pull-review clean-ups
Removes obsolete flags from rdoc
Updates code sample in README
Starts to clean up the spec_helper and requires.
Adds ability to read the file data stream.

I was indisciplined and there are other refactorings and test improvements
in here as well as the new functionality.
Quoting changes (pull-review)
Pull-review inspired refactoring

Attempts to reduce the complexity of the chunks of the test.
Minor clean-up of tests.

Use POODR principles to check that the File object is doing what it's
responsible for, and not checking the values in the header's response.
Adds a comment about the header's data
Various small clean-ups

No structural or logical changes.

* Some assertions have comment strings to be more informative.
* Changes to make pull-review quieter.