Fixed document error, it should be C compiler.

peixinchen · web-flow · commit 843a7a51cac9 · 2016-08-22T11:40:59.000+08:00
diff --git a/README.md b/README.md
@@ -99,7 +99,7 @@ Build
 
 If librdkafka is installed in a non-standard location provide the include and library directories with:
 
-    $ CPLUS_INCLUDE_PATH=/path/to/include LIBRARY_PATH=/path/to/lib python setup.py ...
+    $ C_INCLUDE_PATH=/path/to/include LIBRARY_PATH=/path/to/lib python setup.py ...
 
 
 Tests
