wildcard major version to latest X.y..z

added check in install function so that if only the major version number is specified, the latest version of that will be installed

fixes 214

src/nvm.go

@@ -168,7 +168,13 @@ func install(version string, cpuarch string) {
     version = reg.ReplaceAllString(re.FindString(content),"")
   }
 
-  version = cleanVersion(version)
+  // if the user specifies only the major version number then install the latest
+  // version of the major version number
+  if len(version) == 1 {
+    version = findLatestSubVersion(version)
+  } else {
+    version = cleanVersion(version)
+  }
 
   if CheckVersionExceedsLatest(version) {
   	fmt.Println("Node.js v"+version+" is not yet released or available.")
@@ -286,6 +292,15 @@ func uninstall(version string) {
   return
 }
 
+func findLatestSubVersion(version string) string {
+	url := web.GetFullNodeUrl("latest-v" + version + ".x" + "/SHASUMS256.txt")
+	content := web.GetRemoteTextFile(url)
+	re := regexp.MustCompile("node-v(.+)+msi")
+	reg := regexp.MustCompile("node-v|-x.+")
+	latest := reg.ReplaceAllString(re.FindString(content), "")
+	return latest
+}
+
 func cleanVersion(version string) string {
   re := regexp.MustCompile("\\d+.\\d+.\\d+")
   matched := re.FindString(version)