Keep glbally activated pandas2ri until all functions wrapped

Change-Id: I775c32b120162f04bef72eec2aa89f421fa805e4
diff --git a/KorAPClient/__init__.py b/KorAPClient/__init__.py
index 9646d68..8bb5f5f 100644
--- a/KorAPClient/__init__.py
+++ b/KorAPClient/__init__.py
@@ -14,6 +14,8 @@
 if version.parse(KorAPClient.__version__) < version.parse(CURRENT_R_PACKAGE_VERSION):
     warnings.warn("R-package RKorAPClient version " + KorAPClient.__version__  + " is outdated, please update.", DeprecationWarning)
 
+pandas2ri.activate()
+
 # noinspection PyPep8Naming
 class KorAPConnection(RS4):
     """Connection to a KorAP server."""