Add skip_crds option to helm (#349)

This adds an option to skip the installation of CRDs when installing or
upgrading a chart.

Closes: #296

molecule/default/roles/helm/files/test-crds/Chart.yaml

@@ -0,0 +1,5 @@
+apiVersion: v2
+name: test-crds
+description: A chart with CRDs
+type: application
+version: 0.1.0

molecule/default/roles/helm/files/test-crds/crds/crd.yaml

@@ -0,0 +1,21 @@
+apiVersion: apiextensions.k8s.io/v1
+kind: CustomResourceDefinition
+metadata:
+  name: foos.example.com
+spec:
+  group: example.com
+  versions:
+    - name: v1
+      served: true
+      storage: true
+      schema:
+        openAPIV3Schema:
+          type: object
+          properties:
+            foobar:
+              type: string
+  scope: Namespaced
+  names:
+    plural: foos
+    singular: foo
+    kind: Foo