[units] Add new unit conversion module

Only does temperatures right now.
TODO: Length, volume, mass

units.py

@@ -0,0 +1,45 @@
+# -*- coding: utf8 -*-
+"""
+units.py - Unit conversion module for Willie
+Copyright © 2013, Elad Alfassa, <[email protected]>
+Licensed under the Eiffel Forum License 2.
+
+"""
+from willie.module import command, example
+import re
+
+find_temp = re.compile('([0-9]*\.?[0-9]*)[ °]*(K|C|F)',  re.IGNORECASE)
+
+def f_to_c(temp):
+    return (float(temp) - 32) * 5/9
+
+def c_to_k(temp):
+    return temp + 273.15
+
+def c_to_f(temp):
+    return (9.0/5.0 * temp + 32)
+
+def k_to_c(temp):
+    return temp - 273.15
+
+
+@command('temp')
+@example('.temp 100F')
+def temperature(bot, trigger):
+    """
+    Convert temperatures
+    """
+    source = find_temp.match(trigger.group(2)).groups()
+    unit = source[1].upper()
+    numeric = float(source[0])
+    celsius = 0
+    if unit == 'C':
+        celsius = numeric
+    elif unit == 'F':
+        celsius = f_to_c(numeric)
+    elif unit == 'K':
+        celsius = k_to_c(numeric)
+
+    kelvin = c_to_k(celsius)
+    fahrenheit = c_to_f(celsius)
+    bot.reply("%s°C = %s°F = %s°K" % (celsius, fahrenheit, kelvin))