IssueRequest struct for create/edit. Fixes #75.

Using an *Issue in IssuesService.{Create,Edit} means that the Labels
and Assignee fields do not serialize to the correct JSON representation
for the GitHub API. This change introduces an IssueRequest struct to
use instead, allowing labels and assignees to be set on create or edit.
add Alex Bramley as contributor

(Alex is a Googler, so no change to AUTHORS file)
Add support for getting repository README files.
Add Ali Afshar to as contributor

(Ali is a Googler, so no change to AUTHORS file)
add support for auditing 2FA of org members

This is a BREAKING CHANGE due to the change in the ListMembers method
signature.
create temp file for repo release test

This is primarily needed to allow the test to run unmodified in certain
specialized environments (namely, Google's build clusters)
include full text of creative commons license
add State field to IssueRequest
add ListOptions field to ListMembersOptions
Add URL and HTMLURL to Issue

Signed-off-by: Ondrej Kupka <ondra.cap@gmail.com>
Implement support for RepositoriesService ListContributors
add Chris Schaefer as contributor
travis: test on go 1.2 and tip
Add support for RepositoriesService ListBranches
Make HTMLURL accessible on user struct
add Tobias Schmidt (of SoundCloud) as contributor
Added code for the Content API

With this code it should be possible to tick the ‘Content’ box in issue
#37. The code is written after reviewing PR #64 and so is (very)
loosely based on that PR. So big thanks for the work already done by
@octavore! I did however had some different insights about a few fixes
and as the PR hasn’t moved for the last 5 months, I thought to just
rewrite and PR and I send in a new PR hoping to come to a merge…
add Sander van Harmelen as contributor
Correct type name in the doc example
add Hari haran as a contributor