implements feature to list {all gists : authed user} & {public gists : non-authed user}
edit README file with use case for listing gists
change result format, shows filenames now

> shows file name instead of description
> change optparse block in bin/gist
changes output format to be used programatically

> removed header lines for public and private gists.
handles middle exceptions using Gist::Error

> now exceptions in middle of execution goes to 'rescue' and exit with
  status 1
add method to handle access token internally

> new method 'auth_token' returns access token string, if it exists or
  returns 'nil' if access token file is not there.
Merge commit 'refs/pull/176/head' of github:defunkt/gist
Minor fmt
More concrete example
Tidy up output a little