Create CLI tool & Readme updates

Create a simple CLI tool that allows you to create shares of files and
recombine them. Document how to use it and the library.

Add goreleaser so I can release binaries for easy installation for
people who want to test this.

.gitignore

@@ -0,0 +1,3 @@
+bin
+dist
+tmp

.goreleaser.yml

@@ -0,0 +1,27 @@
+# This is an example goreleaser.yaml file with some sane defaults.
+# Make sure to check the documentation at http://goreleaser.com
+before:
+  hooks:
+    # You may remove this if you don't use go modules.
+    - go mod download
+builds:
+  - main: ./cmd/adss/adss.go
+    env:
+      - CGO_ENABLED=0
+archives:
+- replacements:
+    darwin: Darwin
+    linux: Linux
+    windows: Windows
+    386: i386
+    amd64: x86_64
+checksum:
+  name_template: 'checksums.txt'
+snapshot:
+  name_template: "{{ .Tag }}-next"
+changelog:
+  sort: asc
+  filters:
+    exclude:
+    - '^docs:'
+    - '^test:'

Makefile

@@ -26,6 +26,9 @@ $(BIN)/%: | $(BIN) ; $(info $(M) building $(PACKAGE)…)
 		|| ret=$$?; \
 	   git checkout go.mod go.sum; exit $$ret
 
+GORELEASER = $(BIN)/goreleaser
+$(BIN)/goreleaser: PACKAGE=github.com/goreleaser/goreleaser
+
 GOIMPORTS = $(BIN)/goimports
 $(BIN)/goimports: PACKAGE=golang.org/x/tools/cmd/goimports
 
@@ -56,7 +59,7 @@ check: check-fmt test-race ## Run all checks
 
 .PHONY: clean
 clean: ; $(info $(M) cleaning…)	@ ## Cleanup everything
-	$Q rm -rf $(BIN)
+	$Q rm -rf $(BIN) dist
 
 .PHONY: help
 help:
@@ -66,3 +69,15 @@ help:
 .PHONY: version
 version:
 	@echo $(VERSION)
+
+.PHONY: bin/adss
+bin/adss: ## Build the adss binary to bin/adss
+	$(GO) build -o ./bin/adss ./cmd/adss
+
+.PHONY: release/latest
+release-latest: | $(GORELEASER) ## Compile and release the latest version
+	$(GORELEASER) --snapshot
+
+.PHONY: release/test
+release-test: | $(GORELEASER) @ ## Test creating a release build
+	$(GORELEASER) --snapshot --skip-publish --rm-dist

README.md

@@ -1,7 +1,72 @@
 # Adept Secret Sharing (ADSS)
 
-An example implementation of adept secret sharing (ADSS) as described by
-Bellare, Dai and Rogaway.
+A CLI tool and library implementation of dept secret sharing (ADSS) as described
+by Bellare, Dai and Rogaway.
+
+## Usage
+
+### CLI
+
+Install by downloading pre-build binaries on the releases pages or it install
+from source with `go install github.com/jakecraige/adss`.
+
+```sh
+# Split the secret into a 2-of-3 sharing. First we create a file with the
+# secret, it can be of any type, not just txt.
+$ echo "some secret" > /tmp/secret.txt
+$ bin/adss split -threshold 2 -count 3 -out-dir /tmp -secret-path secret.txt
+Share written to: tmp/share-0.json
+Share written to: tmp/share-1.json
+Share written to: tmp/share-2.json
+Complete.
+
+# We can recover by providing all shares. It prints to stdout in base64 by
+# default, so we decode it with base64 for this example.
+$ bin/adss recover --share-paths /tmp/share-0.json,/tmp/share-1.json,/tmp/share-2.json | base64 -d
+some secret
+
+# We can also store the result in a file
+$ bin/adss recover --share-paths /tmp/share-0.json,/tmp/share-1.json,/tmp/share-2.json -out-path /tmp/recovered-secret.txt
+$ cat /tmp/recovered-secret.txt
+some secret
+
+# We can also recover by providing only two
+$ bin/adss recover --share-paths /tmp/share-0.json,/tmp/share-1.json | base64 -d
+some secret
+
+# If we manually modify the secret value of one of the shares and attempt
+# recovery, we are warned about the invalid share but we still recover it.
+$ bin/adss recover --share-paths /tmp/share-0.json,/tmp/share-1.json,/tmp/share-2-modified.json | base64 -d
+WARN: Invalid share at ./tmp/share-2-modified.json
+some secret
+```
+
+### Library
+
+```golang
+// Split the secret into shares. The shares can be json serialized with the
+// golang marshaller to be persisted on disk.
+as := adss.NewAccessStructure(2, 3)
+secret := []byte("the secret")
+ad := []byte("the associated data")
+shares, err := adss.Share(as, secret, ad)
+if err != nil {
+  return err
+}
+
+// Given a set of shares, attempt to recover the secret. If it can be recovered
+// it returns the secret and the set of shares that were valid inputs. If it
+// cannot be recovered, an error is returned.
+secret, validShares, err := adss.Recover(shares)
+if err != nil {
+  return err
+}
+
+fmt.Printf("%s", secret)
+if len(validShares) < len(shares) {
+  fmt.Println("Some shares were invalid")
+}
+```
 
 ## Security