Fixed issue with counties TopoJSON, moved Pandas dependency to geo_data only

Author: wrobstory

examples/data/us_counties_20m_topo.json

@@ -11,7 +11,6 @@
 from __future__ import division
 import codecs
 import json
-import pandas as pd
 from jinja2 import Environment, PackageLoader
 from pkg_resources import resource_string, resource_filename
 import utilities
@@ -512,6 +511,8 @@ def json_style(style_cnt, line_color, line_weight, line_opacity,
         #Get Data binding pieces if available
         if data is not None:
 
+            import pandas as pd
+
             #Create DataFrame with only the relevant columns
             if isinstance(data, pd.DataFrame):
                 data = pd.concat([data[columns[0]], data[columns[1]]], axis=1)