dygraph-utils.js: isElementContainedBy -> isNodeContainedBy

This fixes a type nit when using the Closure Compiler, since walking
parentNode can give an Element or Document node, not just an Element.
dygraph-tickers.js: Fix variable redeclaration
dygraph-utils.js: Remove trailing white space
dygraph-utils.js: Make Dygraph.error and Dygraph.update public

These seem like reasonable utility functions, and they were used outside
of Dygraph (specifically in DygraphOptions). Making these non-private
resolves Closure Compiler warnings inside dygraph-options.js.
Make dygraph-options.js warning-free under Closure Compiler
BUGFIX: xAxisLabelHeight is set to 0 in case the option 'drawXAxis' is
set to false.
Merge pull request #233 from lucasbergman/master

some small Closure-cleanliness fixes
TEST: Added automated test proving the bugfix made.
TEST: Added example of range selector without the chart.
BUGFIX: Fixed typo
Merge pull request #242 from sauter-hq/draw-xaxis-bugfix

BUGFIX: RangeSelector: xAxisLabelHeight is set to 0 in case the option 'drawXAxis' is set to false.
Merge commit '5605628cc2f2ca8d4f3b297a3d15dbded2c07f1e'