Implement a custom HystrixPropertiesStrategy plugin

Add a custom HystrixPropertiesStrategy implementation where getCommandPropertiesCacheKey is overridden to return null so that HystrixPropertiesFactory will always generate a new HystrixCommandProperties for each new HystrixCommand instantiation.
Back with Scalameter benches :)

```
[info] - execution.generating the properties anew.Test-0 measurements:
[info]     (mean = 0.12 ms, ci = <0.10 ms, 0.14 ms>, significance = 1.0E-10)

[info] - execution.generating the JSON cacheKey.Test-1 measurements:
[info]     (mean = 0.04 ms, ci = <0.03 ms, 0.05 ms>, significance = 1.0E-10)
```

So even with the use of reflection, generating the cachekey is still 3 times faster than generating a fresh one through a call to `new HystrixPropertiesCommandDefault`, with a much narrower confidence interval to boot.