Squid helm chart should offer Deployement label setting

[tmeltser]

Currently there is no option in the helm chart to add label to the deployment (or rather to the pods of the deployment), and it is needed in some cases.

I suggest to add the following:
values.yaml:
.
.
.

podLabels:
  some-label-name-1: some-label-value-1
  some-label-name-2: some-label-value-2

deployment.yaml:

spec:
.
.
.
  template:
    metadata:
      labels:
        app: {{ template "squid.name" . }}
        release: {{ .Release.Name }}
        **{{- if .Values.podLabels }}
          {{ toYaml .Values.podLabels | indent 8 }}
        {{- end }}**

[tmeltser]

I'm ready with a PR if someone is willing to review and integrate it...