Refactor control add_item, allow section overrides

By refactoring the logic to construct the args passed into $wp_customize->add_setting
and $wp_customize->add_control, less duplicated logic is in the controls.
With the control args array now constructed in one place, this gives the
opportunity to introduce a new element field 'section' that can override
the default group that a control is assigned to. This is ideal if you want
the styles controls to be located within existing sections (which I do).
Delete unintentionally added file
Ensure trailing slash for customize-preview-js src

On a multisite subdirectory install, for a site 'foo', a URL
like the following results in a NOBLOGREDIRECT:

http://example.com/foo?styles-action=customize-preview-js...

This results in the preview not working at all. The fix is to ensure
that the script path ends in a slash, and this helps WordPress Multisite
properly route the request to the current site.
Eliminate section overrides and remove prefix from group id
Prevent override of previously-added section
Store default setting value from JSON element

Currently the default value remains blank, so it does not show up in the controls
Improve handling of defaults for compound settings
Typecast foreach loops as (array) to avoid warnings of no plugins or settings returned. Props @pictureitsolved on http://go.brain.st/181HisI
Version bump
Merge branch 'r/1.0.10'
Merge branch 'r/1.0.10' into develop
Rebuild CSS every time customizer saves
Merge pull request #26 from x-team/issue-25-step-behind-styles

Rebuild CSS when Customizer saves. Major props @westonruter!
Merge branch 'develop' of github.com:stylesplugin/styles into develop
Add styles_customize_init action. Proposed response to #24.
Merge pull request #18 from x-team/add-item-refactor-section-override

Refactor control add_item, facilitate adding to existing sections, fix default control values. Note: will revert change to `styles-helpers.php` and move to new issue.
Merge branch 'master' of github.com:stylesplugin/styles
Merge branch 'master' into develop
Revert prefix change from pull request #18
Merge branch 'inline-js-preview' of github.com:x-team/wp-styles into x-team-inline-js-preview

Conflicts:
	classes/styles-customize.php
	classes/styles-plugin.php