Update codegangsta/cli

To fix #122.
IsSet() doesn't return true even when env variables are set.

vendor/github.com/codegangsta/cli/.travis.yml

@@ -1,13 +1,39 @@
 language: go
+
 sudo: false
 
+cache:
+  directories:
+  - node_modules
+
 go:
-- 1.0.3
-- 1.1.2
-- 1.2.2
-- 1.3.3
+- 1.2.x
+- 1.3.x
 - 1.4.2
+- 1.5.x
+- 1.6.x
+- 1.7.x
+- master
+
+matrix:
+  allow_failures:
+  - go: master
+  include:
+  - go: 1.6.x
+    os: osx
+  - go: 1.7.x
+    os: osx
+
+before_script:
+- go get github.com/urfave/gfmrun/... || true
+- go get golang.org/x/tools/... || true
+- if [ ! -f node_modules/.bin/markdown-toc ] ; then
+    npm install markdown-toc ;
+  fi
 
 script:
-- go vet ./...
-- go test -v ./...
+- ./runtests gen
+- ./runtests vet
+- ./runtests test
+- ./runtests gfmrun
+- ./runtests toc