Synchronize get_all_snapshots() with current version of API
typo

s/immitates/imitates/
Re-raise the last exception in the current scope.

`raise` with no arguments finds the last exception in the active scope; this
is the correct way to re-raise an exception that is caught but not handled.
Raising the caught exception object obscures stack information (like line
number) that may be useful for debugging.
Tests for #1554, remove unneeded compatibility layer
- support ami registration with a snapshot ID
Merge pull request #1850 from rjschwei/registerWithSnap

Update EC2 get_all_snapshots and registering an image with a snapshot. Fixes #1850.