ci: switches release process to gh actions and goreleaser (#87)

Also preserves coveralls and appveyor. Closes #58

.goreleaser.yml

@@ -0,0 +1,48 @@
+# This is an example .goreleaser.yml file with some sane defaults.
+# Make sure to check the documentation at http://goreleaser.com
+project_name: git-chglog
+
+before:
+  hooks:
+    # You may remove this if you don't use go modules.
+    - go mod download
+
+builds:
+  - dir: cmd/git-chglog
+    env:
+      - CGO_ENABLED=0
+    goos:
+      - linux
+      - windows
+      - darwin
+    goarch:
+      - amd64
+      - arm
+      - arm64
+    goarm:
+      - 6
+
+archives:
+  - format_overrides:
+      - goos: windows
+        format: zip
+
+checksum:
+  name_template: 'checksums.txt'
+
+changelog:
+  sort: asc
+
+snapshot:
+  name_template: "{{ .Tag }}-next"
+
+brews:
+  - tap:
+      owner: git-chglog
+      name: homebrew-git-chglog
+    homepage: "https://godoc.org/github.com/git-chglog/git-chglog"
+    description: "CHANGELOG generator implemented in Go (Golang)."
+    test: |
+      system "#{bin}/git-chglog --help"
+    install: |
+      bin.install "git-chglog"