Update README.md

Adding a missing comma to the visualization example usage.
What does this do
Add further syntax highlighting
Merge pull request #136 from dzello/master

Add further syntax highlighting to README
Merge pull request #135 from picklepete/patch-1

Update README.md
Add custom funnel demo to /examples/visualize, [ci skip]
Merge branch 'master' of https://github.com/keenlabs/keen-js
Update Google Charts package to v1.1
Fixes #138 (memory leak) and fixes #134 (loading indicator)
Merge pull request #141 from keenlabs/update/google-memory

Fix viz lib memory leak
v3.0.8 release
add test case for keen.once keenlabs#142
Fix #off method, fixes #142
Merge pull request #145 from keenlabs/pr-off-event

Fix #off event method