Complete dygraphs millisecond PR & re-depend upon dygraphs as dependency

[jaredscheib]

• write unit test for [tickers] add milliseconds granularity danvk/dygraphs#777
• test Chronograf against new dygraphs master as dependency, instead of our fork
• publish new dygraphs package on npm
• update Chronograf to depend on newly published dygraphs

[lukevmorris]

Pending PR: danvk/dygraphs#893