fix(kubectl): krew action does not work

The currently deployed release workflow does not work. The template file
for krew does not get translated correctly.

This is an attempt to fix this issue

```
11:42 $ docker run -v $PWD/.krew/profefe.yaml:/tmp/template-file.yaml rajatjindal/krew-release-bot:v0.0.37   krew-release-bot template --tag v0.3.0 --template-file /tmp/template-file.yaml > /tmp/ciao
time="2020-04-05T09:43:35Z" level=info msg="getting sha256 for https://github.com/profefe/kube-profefe/releases/download/v0.3.0/kube-profefe_v0.3.0_Darwin_x86_64.tar.gz"
time="2020-04-05T09:44:03Z" level=info msg="downloaded file /tmp/266050939/1586079815"
time="2020-04-05T09:44:03Z" level=info msg="getting sha256 for https://github.com/profefe/kube-profefe/releases/download/v0.3.0/kube-profefe_v0.3.0_Linux_x86_64.tar.gz"
time="2020-04-05T09:44:40Z" level=info msg="downloaded file /tmp/965187230/1586079843"
time="2020-04-05T09:44:40Z" level=fatal msg="failed to get plugin name from processed template.\nerr: error converting YAML to JSON: yaml: line 19: did not find expected '-' indicator"

```

Signed-off-by: Gianluca Arbezzano <gianarb92@gmail.com>

.krew/profefe.yaml

@@ -3,7 +3,7 @@ kind: Plugin
 metadata:
   name: profefe
 spec:
-  version: { { .TagName } }
+  version: {{ .TagName }}
   homepage: https://github.com/profefe/kube-profefe
   shortDescription: Gather and manage pprof profiles from running pods
   description: |
@@ -16,8 +16,7 @@ spec:
         matchLabels:
           os: darwin
           arch: amd64
-      uri: "https://github.com/profefe/kube-profefe/releases/download/{{ .TagName }}/kube-profefe_{{ .TagName }}_Darwin_x86_64.tar.gz"
-      sha256: a2dd151fcaf3b7e4341986c6cc2726e0dccc69d634fc96a0ac97f8b03ad930a5
+      {{addURIAndSha "https://github.com/profefe/kube-profefe/releases/download/{{ .TagName }}/kube-profefe_{{ .TagName }}_Darwin_x86_64.tar.gz" .TagName }}
       bin: kubectl-profefe
       files:
         - from: kubectl-profefe
@@ -28,8 +27,7 @@ spec:
         matchLabels:
           os: linux
           arch: amd64
-      uri: "https://github.com/profefe/kube-profefe/releases/download/{{ .TagName }}/kube-profefe_{{ .TagName }}_Linux_x86_64.tar.gz"
-      sha256: b68479389df557dd29abd42268fdd9fc22b522a1dfe97458bfb5f804da1f6445
+      {{addURIAndSha "https://github.com/profefe/kube-profefe/releases/download/{{ .TagName }}/kube-profefe_{{ .TagName }}_Linux_x86_64.tar.gz" .TagName }}
       bin: kubectl-profefe
       files:
         - from: kubectl-profefe