Add homebrew and reduce generated CPU architectures for release

Fixes #21
Updates #16

Signed-off-by: Nick Young <ynick@vmware.com>

Author: youngnick

.goreleaser.yml

@@ -9,6 +9,8 @@ builds:
   - windows
   - linux
   - darwin
+  goarch:
+  - amd64
 release:
   github:
     owner: projectcontour
@@ -21,6 +23,13 @@ archives:
     windows: Windows
     386: i386
     amd64: x86_64
+brews:
+- name: ir2proxy
+  github:
+    owner: projectcontour
+    name: homebrew-ir2proxy
+  homepage: "https://github.com/projectcontour/ir2proxy"
+  description: "A tool to convert Contour's IngressRoute resources to HTTPProxy resources."
 checksum:
   name_template: 'checksums.txt'
 snapshot: