Added the ability to quote users texts by chat.

quotes_set does the job of saving users quotes by using the following
command:

  !addquote text to be quoted

quotes_get retrieve quotes stored by using `!quote` command.

plugins/quotes_get.lua

@@ -0,0 +1,37 @@
+do
+  local quotes_file = './data/quotes.lua'
+  local quotes_table
+
+  function read_quotes_file()
+    local f = io.open(quotes_file, "r+")
+
+    if f == nil then
+      serialize_to_file({}, quotes_file)
+    else
+      f:close()
+    end
+    return loadfile (quotes_file)()
+  end
+
+  function get_quote(msg)
+    local to_id = tostring(msg.to.id)
+    local quotes_phrases
+
+    quotes_table   = read_quotes_file()
+    quotes_phrases = quotes_table[to_id]
+
+    return quotes_phrases[math.random(1,#quotes_phrases)]
+  end
+
+  function run(msg, matches)
+    return get_quote(msg)
+  end
+
+  return {
+    description = "retrieves random quotes",
+    usage = "!quote",
+    patterns = {
+      "^!quote$"},
+      run = run
+    }
+end

plugins/quotes_set.lua

@@ -0,0 +1,56 @@
+do
+  local quotes_file = './data/quotes.lua'
+  local quotes_table
+
+  function read_quotes_file()
+    local f = io.open(quotes_file, "r+")
+
+    if f == nil then
+      print ('Created a new quotes file on '..quotes_file)
+      serialize_to_file({}, quotes_file)
+    else
+      print ('Quotes loaded: '..quotes_file)
+      f:close()
+    end
+    return loadfile (quotes_file)()
+  end
+
+  function save_quote(msg)
+    local to_id = tostring(msg.to.id)
+    local quotes
+    local phrase
+
+    phrase   = string.match(msg.text, "!addquote (.+)")
+    if (phrase == nil) then
+      return "Usage: !addquote quote"
+    end
+
+    if quotes_table == nil then
+      quotes_table = {}
+    end
+
+    if quotes_table[to_id] == nil then
+      print ('New quote key to_id: '..to_id)
+      quotes_table[to_id] = {}
+    end
+
+    quotes = quotes_table[to_id]
+    quotes[#quotes+1] = phrase
+
+    serialize_to_file(quotes_table, quotes_file)
+
+    return "done!"
+  end
+
+  function run(msg, matches)
+    quotes_table = read_quotes_file()
+    return save_quote(msg)
+  end
+
+  return {
+    description = "Save quote",
+    usage       = "!addquote (quote)",
+    patterns    = {"^!addquote (.+)$"},
+    run = run
+  }
+end