Username cachine and various fixes.

Usernames seen by the bot are now cached in the $usernames table. To get the ID associated with a
username, use the resolve_username() function from utilities.lua.
The table_size() function in utilities.lua will tell you the number of items in a key/pair table.
about.lua no longer displays a link preview in the about message.
currency.lua now accepts decimal arguments for the amount.
luarun.lua now correctly displays "false" return values.
moderation.lua will no longer send "I do not administrate this group".

utilities.lua

@@ -1,7 +1,8 @@
 -- utilities.lua
 -- Functions shared among plugins.
 
-function get_word(s, i) -- get the indexed word in a string
+ -- get the indexed word in a string
+get_word = function(s, i)
 
 	s = s or ''
 	i = i or 1
@@ -15,7 +16,8 @@ function get_word(s, i) -- get the indexed word in a string
 
 end
 
-function string:input() -- Returns the string after the first space.
+ -- Returns the string after the first space.
+function string:input()
 	if not self:find(' ') then
 		return false
 	end
@@ -57,14 +59,16 @@ local lc_list = {
 	['!'] = 'ǃ'
 }
 
-function latcyr(str) -- Replaces letters with corresponding Cyrillic characters.
+ -- Replaces letters with corresponding Cyrillic characters.
+latcyr = function(str)
 	for k,v in pairs(lc_list) do
 		str = string.gsub(str, k, v)
 	end
 	return str
 end
 
-function load_data(filename) -- Loads a JSON file as a table.
+ -- Loads a JSON file as a table.
+load_data = function(filename)
 
 	local f = io.open(filename)
 	if not f then
@@ -78,7 +82,8 @@ function load_data(filename) -- Loads a JSON file as a table.
 
 end
 
-function save_data(filename, data) -- Saves a table to a JSON file.
+ -- Saves a table to a JSON file.
+save_data = function(filename, data)
 
 	local s = JSON.encode(data)
 	local f = io.open(filename, 'w')
@@ -88,7 +93,7 @@ function save_data(filename, data) -- Saves a table to a JSON file.
 end
 
  -- Gets coordinates for a location. Used by gMaps.lua, time.lua, weather.lua.
-function get_coords(input)
+get_coords = function(input)
 
 	local url = 'http://maps.googleapis.com/maps/api/geocode/json?address=' .. URL.escape(input)
 
@@ -107,4 +112,31 @@ function get_coords(input)
 		lon = jdat.results[1].geometry.location.lng
 	}
 
+end
+
+ -- Get the number of values in a key/value table.
+table_size = function(tab)
+
+	local i = 0
+	for k,v in pairs(tab) do
+		i = i + 1
+	end
+	return i
+
+end
+
+resolve_username = function(target)
+ -- If $target is a known username, returns associated ID.
+ -- If $target is an unknown username, returns nil.
+ -- If $target is a number, returns that number.
+ -- Otherwise, returns false.
+
+	local input = tostring(target):lower()
+	if input:match('^@') then
+		local uname = input:gsub('^@', '')
+		return usernames[uname]
+	else
+		return tonumber(target) or false
+	end
+
 end