Add python support (#9)

support for 3.8 and 3.9

Update tests and requirements (#7)

Adding gcp tests
Use client from `goblet_gcp_client`

Updated branching capabilities (#2)

Supports nested branches.
Fixes some edge cases.

for example: 
```
assign > step_1 > step_2
step_2 > step_3
step_2 > step_4
step_1 > step_5
```
creates 
```
main:
  steps:
  - init:
      assign:
      - test: test
  - step_1:
      call: http.post
      args:
        url: ${"https://us-central1-" + args.project_id + ".cloudfunctions.net/step1"}
  - branch-2:
      parallel:
        branches:
        - step_2_branch:
            steps:
            - step_2:
                call: http.post
                args:
                  url: ${"https://us-central1-" + args.project_id + ".cloudfunctions.net/step2"}
                  body:
                    var: ${var1}
        - step_5_branch:
            steps:
            - step_5:
                call: http.post
                args:
                  url: ${"https://us-central1-" + args.project_id + ".cloudfunctions.net/step5"}
  - branch-1:
      parallel:
        branches:
        - step_3_branch:
            steps:
            - step_3:
                call: http.post
                args:
                  url: ${"https://us-central1-" + args.project_id + ".cloudfunctions.net/step3"}
        - step_4_branch:
            steps:
            - step_4:
                call: http.post
                args:
                  url: ${"https://us-central1-" + args.project_id + ".cloudfunctions.net/step4"}
```

Scheduler, multistep, DataformSteps (#1)

* scheduler

```
wf.set_schedule("0 * * * *")
```
* MultiSteps class
* DataformSteps

```
wf = Workflow(WORKFLOW_NAME, serviceAccount=SERVICE_ACCOUNT)
wf.set_schedule("0 * * * *")

assign = AssignStep(
    wf,
    "init",
    repository=f"projects/{PROJECT_ID}/locations/{REPOSITORY_LOCATION}/repositories/{REPOSITORY_ID}",
)

df = DataformSteps(wf, git_branch=DATAFORM_GIT_BRANCH)

assign > df
```

Initial commit