SWIG: add min version of 3.0.5

For version below 3.0.5 python will show error:
    def incr(self, $ignore=1): return _yang.SwigPyIterator_incr(self, $ignore)
                   ^
SyntaxError: invalid syntax

Signed-off-by: Mislav Novakovic <mislav.novakovic@sartura.hr>
diff --git a/swig/CMakeLists.txt b/swig/CMakeLists.txt
index 4d99971..2700340 100644
--- a/swig/CMakeLists.txt
+++ b/swig/CMakeLists.txt
@@ -6,7 +6,7 @@
 
 # find SWIG package
 if(GEN_LANGUAGE_BINDINGS)
-    find_package(SWIG REQUIRED)
+    find_package(SWIG 3.0.5 REQUIRED)
     if(NOT SWIG_FOUND)
         message(WARNING "SWIG library not found")
     else()