feat(refacto): move everything in internal package

This allows to install katenary with `go install` and to clean up the
project folder.

internal/generator/version.go

@@ -0,0 +1,28 @@
+package generator
+
+import (
+	"regexp"
+	"runtime/debug"
+)
+
+// Version is the version of katenary. It is set at compile time.
+var Version = "master" // changed at compile time
+
+// GetVersion return the version of katneary. It's important to understand that
+// the version is set at compile time for the github release. But, it the user get
+// katneary using `go install`, the version should be different.
+func GetVersion() string {
+	// try to get the semantic version from the Version variable (theorically set at compile time)
+	if reg := regexp.MustCompile(`^v?\d+.\d+.\d+.*|^release-.*`); reg.MatchString(Version) {
+		return Version
+	}
+
+	// OK... let's try to get the version from the build info
+	// get the version from the build info (when installed with go install)
+	if v, ok := debug.ReadBuildInfo(); ok {
+		return v.Main.Version + "-" + v.GoVersion
+	}
+
+	// OK... none worked, so we return the default version
+	return Version
+}