Add fuzz.sh to do fuzzing with go-fuzz (#194)

Fixes #181

.gitignore

@@ -1 +1,2 @@
 test_program/test_program_bin
+fuzz/

fuzz.go

@@ -0,0 +1,31 @@
+// +build gofuzz
+
+package toml
+
+func Fuzz(data []byte) int {
+	tree, err := LoadBytes(data)
+	if err != nil {
+		if tree != nil {
+			panic("tree must be nil if there is an error")
+		}
+		return 0
+	}
+
+	str, err := tree.ToTomlString()
+	if err != nil {
+		if str != "" {
+			panic(`str must be "" if there is an error`)
+		}
+		panic(err)
+	}
+
+	tree, err = LoadString(str)
+	if err != nil {
+		if tree != nil {
+			panic("tree must be nil if there is an error")
+		}
+		return 0
+	}
+
+	return 1
+}

fuzz.sh

@@ -0,0 +1,15 @@
+#! /bin/sh
+set -eu
+
+go get github.com/dvyukov/go-fuzz/go-fuzz
+go get github.com/dvyukov/go-fuzz/go-fuzz-build
+
+if [ ! -e toml-fuzz.zip ]; then
+    go-fuzz-build github.com/pelletier/go-toml
+fi
+
+rm -fr fuzz
+mkdir -p fuzz/corpus
+cp *.toml fuzz/corpus
+
+go-fuzz -bin=toml-fuzz.zip -workdir=fuzz