Update codegangsta/cli

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

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

@@ -0,0 +1,24 @@
+version: "{build}"
+
+os: Windows Server 2012 R2
+
+clone_folder: c:\gopath\src\github.com\urfave\cli
+
+environment:
+  GOPATH: C:\gopath
+  GOVERSION: 1.6
+  PYTHON: C:\Python27-x64
+  PYTHON_VERSION: 2.7.x
+  PYTHON_ARCH: 64
+
+install:
+- set PATH=%GOPATH%\bin;C:\go\bin;%PATH%
+- go version
+- go env
+- go get github.com/urfave/gfmrun/...
+- go get -v -t ./...
+
+build_script:
+- python runtests vet
+- python runtests test
+- python runtests gfmrun