refactor context related functions into context.c

Signed-off-by: Andy Green <andy.green@linaro.org>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4df0dfb..d68410d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -262,6 +262,7 @@
 	lib/libwebsockets.c
 	lib/output.c
 	lib/parsers.c
+	lib/context.c
 	lib/sha-1.c
 	)