support additional options for rollingUpdate

[eytan-avisror]

fixes #39

This makes rollingUpdate more usable by making it's options configurable.

[codecov]

Codecov Report

Merging #44 into master will increase coverage by 0.72%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #44      +/-   ##
==========================================
+ Coverage   70.88%   71.61%   +0.72%     
==========================================
  Files           6        6              
  Lines         742      761      +19     
==========================================
+ Hits          526      545      +19     
  Misses        159      159              
  Partials       57       57

Impacted Files	Coverage Δ
...rovisioners/ekscloudformation/ekscloudformation.go	80.26% <100%> (+0.06%)	⬆️
...rollers/provisioners/ekscloudformation/strategy.go	56.52% <100%> (+4.14%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update db31492...8d89ddf. Read the comment docs.

[eytan-avisror]

BDDs passed

Ran 4 of 4 Specs in 1259.401 seconds
SUCCESS! -- 4 Passed | 0 Failed | 0 Pending | 0 Skipped
--- PASS: TestE2e (1259.40s)
PASS
ok  	github.com/keikoproj/instance-manager/test-bdd	1259.799s

[tekenstam]

Looks good, although should add documentation for these new options, perhaps in another PR.