clarify exactly what peep does and doesn't do

I think this text will make it easier for people to understand what peep
does and doesn't do and make it so Erik doesn't have to answer the same
set of questions over and over again.
Merge pull request #25 from willkg/patch-1

clarify exactly what peep does and doesn't do
Punctuation in readme
Fix #26: Figure out wheel file version.

The wheel file spec [0] defines the filename pattern
for wheel archives. This uses that to check package name
and get the version.

Also fix the exception to report the file and package name
on failure.

[0] http://legacy.python.org/dev/peps/pep-0427/#file-name-convention
minor style crap; no behavior changes
Add wheel support to version history. Bump version to 1.0.
Merge wheel support. Close #27.
Credit pmac for wheel support.
Pip replaces '_' in package names with '-' so peep needs to do so in the archive file name version detection.
Fix a typo in the Fearsome Warning.
Refactor version_of_download() to remove repetition and improve symmetry.
Merge support for distros whose names contain underscores. Close #29.
Tweak changelog wording. Fix whitespace.
Address wheels, now the more common motivation for multiple hashes, in the readme.
Add support for .tar.bz2 archives.

Found that at least pytz provides a tar.bz2 archive.
Update version history. Bump version to 1.0.2.
Basic support for Python 3.3
Remove unnecessary str() cast.

decode() is sufficient to turn a bytestring into a string in Python 3. In Python 2, decode() harmlessly returns a unicode.
Update readme and trove classifiers.
Fix formatting in the "expected this, got that" message.