Implement describe_policy and VM::EC2::ScalingPolicy
Various bug and documentation fixes

README          Cluster placement groups are supported
EC2.pm          Doc fixes, associate_route_table() did not pass RouteTableId to API call
Snapshot.pm     When copying snapshots to another region, describe_snapshots() would
                 occasionally not return a value in refresh() when in a wait_for_snapshots()
                 loop.  Now refresh() checks that a new value was returned before assigning to self and
                 returns true if a refresh occurred.
RouteTable.pm   Add route management convenience methods to match docs in VPC.pm
Subnet.pm       create_route_table() now returns RouteTable object as per docs in VPC.pm
Add methods get_signin_token and login_url to enable federated login
Merge branch 'master' of github.com:miquelruiz/LibVM-EC2-Perl
Fixes for latency in objects registering and when request limit is exceeded

New objects don't always appear immediately after request.  Use eval loop
to wait for them to appear.
When RequestLimitExceeded error is returned by API call, go into exponential
backoff retry loop for up to just over a minute.
Merge pull request #13 from miquelruiz/master

AWS Security Token feature working again
Merge pull request #12 from lkinley/master

Various bug and doc fixes
framework for incremental loading written, but methods need to be refactored
default import is to bring in everything
added ami and customer gateway support
Fixed incorrect package declaration for VM::EC2::Instance::State::Reason
partial reorganization; not functional
first phase of conversion complete; untested
regression tests working
added basic parameter parsing module
clean up parameter parsing
begin to rewrite parameter passing for instance methods
instance.pm converted to using new-style parameter parsing
work on documentation
started writing async version of call()