Closure fix; force cast from Element to Node.
Closure tweak: variable 'd' declared twice within the same method.
Closurize dygraph-options.js. Not done.

Also fix bug: this.labels_ was never used! Booo...
Closure fix type Dyraph->Dygraph.
Closurize rgbcolor.js
Some closurifying dygraph-canvas and dygraph-layout.
FEATURE: added test for issue #451
REFACTORING: corrected the name for test "step_plot_per_series"
BUGFIX #451: fixed "connect-separated-points" bug
TEST: adapted test for bugfix
FEATURE: Added support for per-axis grid options and added new option:
"gridLinePattern"
FEATURE: Added documentation of new gridLinePattern and adapted other
grid options
TEST: Added examples of new grid options and features.
TEST: Added automated tests for new grid features.
BUGFIX: Fixed invalid option reference
REFACTORING: Spelling corrections and better documentation.
REFACTORING: Added exception if no y axis has the independentTicks
option activated.
BUG FIX: Changed check to undefined with === as proposed by jslint.
REFACTORING: use the method "getLeftBoundary" instead of a private
variable
BUGFIX: First try of fixing missing data bug for customBars and errorBars