* (feature) Added separate top and bottom padding for title plugin.
* Added regular padding multiplier like how it was before.
* Now makes use of toPadding helper.
Fixed typo in toPadding helper.
* Fixed requested changes.
Chart.layouts seems more consistent with other service names (Chart.plugins, Chart.scales, etc.) but also more inline with the service which handle many layout (one per charts).
For consistency, enable ESLint `one-var` rule to require multiple variable declarations for initialized variables per scope. Uninitialized variables can still be declared together (preferred) or separately.
http://eslint.org/docs/rules/one-var
The title plugin and scale title now accept lineHeight specified using unitless value (1.4), length ('1.4em' or '12px'), percentage ('200%') or keyword ('normal' === 1.2). The line height parsing has been refactored under the 'Chart.helpers.options' namespace. Also fix incorrect text positioning in the title plugin.
https://developer.mozilla.org/en-US/docs/Web/CSS/line-height
Default options can now be accessed by importing `core/core.defaults`. The returned object acts as a singleton and is populated when importing classes that expose their own default values (meaning that importing only `code.defaults` results in an empty object). Also make `Chart.Ticks` and `Chart.Interaction` importable since existing defaults rely on these values.
Add the `defaults._set` method that make easier declaring new defaults by merging given values with existing ones for a specific scope (`global`, `scale`, `bar`, etc).
Properly export helpers and remove dependencies to `Chart.helpers`. Helpers can now be accessed from `src/helpers/index.js` (`var helpers = require('path/to/helpers/index')`, instead of `var helpers = Chart.helpers`).
The `clone` method now accepts any type of input but also recursively perform a deep copy of the array items. Rewrite the `configMerge` and `scaleMerge` helpers which now rely on a new generic and customizable `merge` method, that one accepts a target object in which multiple sources are deep copied. Note that the target (first argument) is not cloned and will be modified after calling `merge(target, sources)`. Add a `mergeIf` helper which merge the source properties only if they do not exist in the target object.
For consistency with `valueOrDefault`, `valueAtIndexOrDefault` now returns null if `value` (expected array) is null. Also get rid of the superfluous `get` prefix in `getValueOrDefault` and `getValueAtIndexOrDefault`.
