fix travis build

.travis.yml

@@ -14,6 +14,8 @@ cache:
 
 before_script:
   - go get github.com/urfave/cli/flag-gen || true
+  - go get github.com/shurcooL/vfsgen || true
+  - go get github.com/shurcooL/httpfs/union || true
   - go get github.com/urfave/gfmrun/... || true
   - go get golang.org/x/tools/cmd/goimports
   - if [ ! -f node_modules/.bin/markdown-toc ] ; then
@@ -21,7 +23,7 @@ before_script:
     fi
 
 script:
-  - go generate ./...
+  #- go generate ./... # to be uncommented after merge as we cannot compile the package which is not present in master
   - ./runtests vet
   - ./runtests test
   - ./runtests gfmrun