First commit.
Update standard package list to Go 1.2.
Add custom service for Gists, use GitHub API and set additional metainfo.

It populates Gist-specific metainfo like ProjectURL, BrowseURL for
files and root folder, and LineFmt.
It uses GitHub API rather than git commands (thus it'll work in Google
App Engine).
Use the file contents provided in first GH API call.

There is no need to fetch the files individually since they're already
provided.
Use gitHubCred for GitHub API call; fix LineFmt.
Use expand to construct the gist URL.
Handle present function flags.

This change fixes presentations that use the .code -edit and -numbers
flags.
Set user-agent on all requests.
Include forks in GitHub updates.
Remove GitHub credentials, user agent.

Applications can use the http.Client to implement authentication, set
the user agent string, implement timeouts and so on. These details do
not need to be part of this package.