Fix GitHub tag links, and add missing ones.
Merge pull request #1523 from zessx/patch-1

Fix GitHub tag links, and add missing ones.
Add a deprecation warning for using units in rgba/hsla alpha parameters.

See #1525
Fix a couple test errors.
Bump VERSION to 3.4.8.
Fixed a type in documentation

SassScript now supports **seven** data types since 3.3, not *six*.
Merge pull request #1526 from HugoGiraudel/stable

Fixed a typo in documentation
adding appveyor configuration to this branch off stable
use a larger build matrix

new versions of Ruby (with DevKit) have been installed:
  - 1.9.3 x86 (C:\Ruby193 - default in PATH)
  - 2.0.0 x86 (C:\Ruby200)
  - 2.0.0 x64 (C:\Ruby200-x64)