Move VerifyBootstrapInit from Environ.Bootstrap implementations into environs.Bootstrap.
Format.
Remove some code that becomes unnecessary with instance type selection.
Merge trunk, resolve conflict.
Tests for methods I want to add.  I'm not planning to satisfy the Endpoint tests in this branch, but requirements of the next step are clear-cut so might as well specify them.
Stub implementations, and sketches of the real ones.  Tests: 6 failures.
Satisfy getImageBaseURL test.  Tests: 5 failures.
Satisfy most basic getEndpoint test by hard-coding, and disable the tests for future functionality.  Tests: 2 failures.
Satisfy remaining tests (for getImageStream and getImageSigningRequired) by hard-coding.  We'll make it configurable later.
Move tests to environ_test.go, because the methods are on Environ.
Resolve misunderstanding over the meaning of 'image data signing required' — it's the Simplestreams image metadata, not the images themselves.
Separate storage-consistency attempt strategy from generic shortAttempt.
Suggested bit of documentation from Roger Peppe.
Turns out we don't need Min: 1 on AttemptStrategy.  It always tries at least once.
Review changes.
Merge trunk.
Merge predecesor branch (now approved, but not landed due to lander outage) and resolve planned-for conflicts.
Make ProxyRoundTripper setup jus a little bit easier.
Document.
Rename VirtualRoundTripper to the more descriptive CannedRoundTripper.