[Issue #383] Adding support for UIAccessibilityElement

Signed-off-by: Mattt Thompson <m@mattt.me>
Merge branch 'master' of github.com:mattt/TTTAttributedLabel
[Issue #383] Reorganizing and refactoring boundingRectForCharacterRange:
[Issue #385] Deprecating leading property, in favor of lineSpacing property
[Issue #376] Fixing alignment and trunctionation issue on last line of text

Signed-off-by: Mattt Thompson <m@mattt.me>
[Issue #380] Taking minimumScaleFactor into account for automatic resizing of text
Replacing __LP64__ macros with more semantic  CGFLOAT_IS_DOUBLE
Bumping version to 1.10.0
Replace deprecated `leading` with `lineSpacing` in README.
Add accessibility documentation to README
Merge pull request #387 from getaaron/fix-lineSpacing-in-README

Replace deprecated `leading` with `lineSpacing` in README.
Merge pull request #386 from getaaron/accessibility-documentation

Add accessibility documentation to README
Minor README copy-editing