fix some file extensions

Task/Echo-server/CoffeeScript/echo-server.coffee

@@ -0,0 +1,17 @@
+net = require("net")
+server = net.createServer (conn) ->
+  console.log "Connection from #{conn.remoteAddress} on port  #{conn.remotePort}"
+  conn.setEncoding "utf8"
+  buffer = ""
+  conn.on "data", (data) ->
+    i = 0
+
+    while i <= data.length
+      char = data.charAt(i)
+      buffer += char
+      if char is "\n"
+        conn.write buffer
+        buffer = ""
+      i++
+
+server.listen 12321, "localhost"