Added a fuzzer for spinnaker package

[AdamKorcz]

Dear maintainers of Chaosmonkey,

I am reaching out to you because I have worked on integrating continous fuzzing into your project by way of OSS-fuzz. Fuzzing is a popular technique that is used to identify security vulnerabilities and bugs in your project. Although fuzzing is mainly known for its effectivenes in low-level languages like C and C++, fuzzing Go code has proven fruitful recently and many other Go projects are already integrated into OSS-fuzz, some of which are Prometheus, Kubernetes, fasthttp, fastjson, grpc-gateway, TiDB.

The fuzzer in this PR is implemented by means of go-fuzz which provides a simple api and is the most popular fuzzer for Go at the moment.

Fuzzers implemented in go-fuzz can be run both locally or continuously through a platform like OSS-fuzz, which is a project run by Google that dedicates hardware to run fuzzers free of charge. While OSS-fuzz is a free service, it is offered with an implied expectation that bugs are fixed and when a bug is found by OSS-fuzz maintainers get sent a link to a detailed bug report by email and the bug report is private for 90 days after which it becomes public.

ADA Logics is a contributor of open source security and we have integrated dozens of projects into OSS-fuzz. All fuzzers in this PR are tested on OSS-fuzz's infrastructure and all we need from your side are the email addresses that should receive the bug reports and then we are happy to complete the integration to OSS-fuzz.

[coveralls]

Coverage remained the same at 54.054% when pulling 5793b2ca65b15c589400008bdf07309e088ffa72 on AdamKorcz:master into 68e3282ef73c39c9ae998185f526cc2713c612d1 on Netflix:master.