268 convert odt file to pdf

Closes https://code.vereign.com/code/restful-api/issues/268

This MR is based on !38 (merged) (Implement pdf signing on the client) and its only change is modification of gopkg.toml file, so that during testing VCL is built against the corresponding restful-api branch.

Gopkg.toml

@@ -25,7 +25,7 @@
 #   unused-packages = true
 
 [[constraint]]
-  branch = "master"
+  branch = "268-convert-odt-file-to-pdf"
   name = "code.vereign.com/code/restful-api"
 
 [prune]