Modified 'candlestick' function in response to request matplotlib#2546

1. Added ability for the candlestick function to use a "light" and "dark" theme
2. Fill color of candlestick bodies can be user definite and is based upon stock price movement on each given period
3. In the light theme (which uses a white background) candlestick shadows are dark; ie: Follows traditional candlestick format
4. In dark theme (which uses black background) candlestick shadows match box colors

lib/matplotlib/finance.py

@@ -306,7 +306,7 @@ def plot_day_summary(ax, quotes, ticksize=3,
 
 
 def candlestick(ax, quotes, width=0.2, colorup='k', colordown='r',
-                alpha=1.0):
+                alpha=1.0, coloredge='k', theme='light'):
 
     """
 
@@ -326,6 +326,8 @@ def candlestick(ax, quotes, width=0.2, colorup='k', colordown='r',
     colorup     : the color of the rectangle where close >= open
     colordown   : the color of the rectangle where close <  open
     alpha       : the rectangle alpha level
+    coloredge   : the color of the rectangle border
+    theme       : specify if using light theme or dark theme (light theme uses a white grid bg, dark uses black grid bg)
 
     return value is lines, patches where lines is a list of lines
     added and patches is a list of the rectangle patches added
@@ -334,33 +336,43 @@ def candlestick(ax, quotes, width=0.2, colorup='k', colordown='r',
 
     OFFSET = width/2.0
 
+    # Adjust candlestick body edges based upon theme
+    if theme == 'light':
+        coloredge = 'k'
+        coloredgeup = 'k'
+        coloredgedown = 'k'
+    else:
+        coloredgeup = colorup
+        coloredgedown = colordown
+
     lines = []
     patches = []
     for q in quotes:
         t, open, close, high, low = q[:5]
 
+        # Make candlestick bodies fill based upon stock price movement for given period
         if close>=open :
             color = colorup
             lower = open
             height = close-open
+            vline = Line2D(xdata=(t, t), ydata=(low, high), color=coloredgeup, linewidth=0.5, antialiased=True, zorder=0)
         else           :
             color = colordown
             lower = close
             height = open-close
+            vline = Line2D(xdata=(t, t), ydata=(low, high), color=coloredgedown, linewidth=0.5, antialiased=True, zorder=0)
 
-        vline = Line2D(
-            xdata=(t, t), ydata=(low, high),
-            color='k',
-            linewidth=0.5,
-            antialiased=True,
-            )
+        # Should look for a better way to do this
+        if theme != 'light':
+            coloredge = color
 
         rect = Rectangle(
             xy    = (t-OFFSET, lower),
             width = width,
             height = height,
             facecolor = color,
-            edgecolor = color,
+            edgecolor = coloredge,
+            zorder=1,
             )
         rect.set_alpha(alpha)