Chaostoolkit-aws

Added

- support for Python 3.7
- support for cloudwatch probes and actions
- support for invoking lambdas
- support for getting and updating lambda timeout and memory size limits
- probe for cloudwatch metric statistics

Changed

- make sure instances with no explicit lifecycle can be stopped. They are
assumed to be in the `normal` lifecycle as per the last
[line of the AWS documentation][]. [25][25]

[25]: https://github.com/chaostoolkit-incubator/chaostoolkit-aws/issues/25
[instlifecycledocs]: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instance-purchasing-options.html

- add probes to wait for auto-scaling group to have healthy/unhealthy instance
and a probe to check if there is any ongoing scaling activity

Changed

- add `elbv2`, `asg` and `awslambda` packages to the setup function so they
get packaged and distributed

Added

Added

- add `count_instances` probe which can be used to count of all instances matching filters
- support for elbv2 with basic probes and action
- support for asg with basic probes
- fix asg probe to support pagination
- support for lambda with basic probes and action

Changed

- Refactoring to support spot instances termination along with cancelling spot request

Added

- Pass filters to `ec2` actions so that specific instances can be selected
for an experiment

Changed

- Remove the irrelevant discover system call