Plugin Refactor to use arbitrary state machines (#1)

Goal:
Propeller should support more types of transitions so that plugin
writers can handle cases where it is not possible to get idempotency
from downstream services. Also provide a simplified API that makes
writing plugins easy.

Done:

New Node handler interface
Implemented Task handler
Implemented Dynamic handler
modified node executor
Unit tests for end to end

.travis.yml

@@ -1,7 +1,7 @@
 sudo: required
 language: go
 go:
-  - "1.12"
+  - "1.13"
 services:
   - docker
 jobs:
@@ -13,9 +13,9 @@ jobs:
       script: make docker_build
     - if: fork = false
       stage: test
-      name: docker build and push
+      name: docker build
       install: true
-      script: make dockerhub_push
+      script: make docker_build
     - stage: test
       install: make install
       name: lint

Dockerfile

@@ -1,10 +1,10 @@
 # WARNING: THIS FILE IS MANAGED IN THE 'BOILERPLATE' REPO AND COPIED TO OTHER REPOSITORIES.
 # ONLY EDIT THIS FILE FROM WITHIN THE 'LYFT/BOILERPLATE' REPOSITORY:
-# 
+#
 # TO OPT OUT OF UPDATES, SEE https://github.com/lyft/boilerplate/blob/master/Readme.rst
 
-# Using go1.10.4
-FROM golang:1.10.4-alpine3.8 as builder
+# Using go1.13.3
+FROM golang:1.13.3-alpine3.10 as builder
 RUN apk add git openssh-client make curl dep
 
 # COPY only the dep files for efficient caching
@@ -25,7 +25,7 @@ RUN make linux_compile
 ENV PATH="/artifacts:${PATH}"
 
 # This will eventually move to centurylink/ca-certs:latest for minimum possible image size
-FROM alpine:3.8
+FROM alpine:3.10
 COPY --from=builder /artifacts /bin
 
 RUN apk --update add ca-certificates