vendor: add mattn/go-shellwords

vendor/github.com/mattn/go-shellwords/README.md

@@ -0,0 +1,47 @@
+# go-shellwords
+
+[![Coverage Status](https://coveralls.io/repos/mattn/go-shellwords/badge.png?branch=master)](https://coveralls.io/r/mattn/go-shellwords?branch=master)
+[![Build Status](https://travis-ci.org/mattn/go-shellwords.svg?branch=master)](https://travis-ci.org/mattn/go-shellwords)
+
+Parse line as shell words.
+
+## Usage
+
+```go
+args, err := shellwords.Parse("./foo --bar=baz")
+// args should be ["./foo", "--bar=baz"]
+```
+
+```go
+os.Setenv("FOO", "bar")
+p := shellwords.NewParser()
+p.ParseEnv = true
+args, err := p.Parse("./foo $FOO")
+// args should be ["./foo", "bar"]
+```
+
+```go
+p := shellwords.NewParser()
+p.ParseBacktick = true
+args, err := p.Parse("./foo `echo $SHELL`")
+// args should be ["./foo", "/bin/bash"]
+```
+
+```go
+shellwords.ParseBacktick = true
+p := shellwords.NewParser()
+args, err := p.Parse("./foo `echo $SHELL`")
+// args should be ["./foo", "/bin/bash"]
+```
+
+# Thanks
+
+This is based on cpan module [Parse::CommandLine](https://metacpan.org/pod/Parse::CommandLine).
+
+# License
+
+under the MIT License: http://mattn.mit-license.org/2017
+
+# Author
+
+Yasuhiro Matsumoto (a.k.a mattn)