Add pandas logo to repo

closes #12911

Author: Michael Droettboom <mdboom@gmail.com>

Closes #12919 from mdboom/add-logo and squashes the following commits:

0cdd1a6 [Michael Droettboom] Add pandas logo to repo

Author: mdboom

README.md

@@ -1,5 +1,5 @@
 <div align="center">
-  <img src="http://pandas.pydata.org/_static/pandas_horizontal_web.png"><br>
+  <img src="https://github.com/pydata/pandas/tree/master/doc/logo/pandas_logo.png"><br>
 </div>
 
 -----------------

doc/logo/pandas_logo.png

@@ -0,0 +1,44 @@
+# script to generate the pandas logo
+
+from matplotlib import pyplot as plt
+from matplotlib import rcParams
+import numpy as np
+
+rcParams['mathtext.fontset'] = 'cm'
+
+
+def fnx():
+    return np.random.randint(5, 50, 10)
+
+
+fig = plt.figure(figsize=(6, 1.25))
+
+ax = fig.add_axes((0.45, 0.1, 0.16, 0.8))
+bar_data = [2.1, -00.8, 1.1, 2.5, -2.1, -0.5, -2.0, 1.5]
+ax.set_ylim(-3, 3)
+ax.set_xticks([])
+ax.set_yticks([])
+ax.bar(np.arange(len(bar_data)), bar_data)
+
+ax = fig.add_axes((0.63, 0.1, 0.16, 0.8))
+for i in range(4):
+    ax.plot(np.random.rand(8))
+ax.set_xticks([])
+ax.set_yticks([])
+
+ax = fig.add_axes((0.63 + 0.18, 0.1, 0.16, 0.8))
+y = np.row_stack((fnx(), fnx(), fnx()))
+x = np.arange(10)
+y1, y2, y3 = fnx(), fnx(), fnx()
+ax.stackplot(x, y1, y2, y3)
+ax.set_xticks([])
+ax.set_yticks([])
+
+plt.figtext(0.05, 0.5, "pandas", size=40)
+
+plt.figtext(
+    0.05, 0.2, r"$y_{it} = \beta^{\prime} x_{it} + \mu_{i} + \epsilon_{it}$",
+    size=16, color="#5a89a4")
+
+fig.savefig('pandas_logo.svg')
+fig.savefig('pandas_logo.png')