Update composer.json

Added dev dependency
Fixed issue with parsing of all nodes match.
@each reduces list before coercing it
Merge pull request #36 from iMoses/master

When passing a list to @each as a variable it acts as a string.
detect recursive mixins
popEnv after compiling/flattening selectors
Use argument inspection to detect native filter effects (grayscale, opacity, invert, saturate)
Merge pull request #44 from robocoder/recursive-mixins

detect recursive mixins
Merge pull request #32 from guilhermeblanco/master

Fixed bug with all match selectors
Merge pull request #43 from robocoder/interpolation-at-root

popEnv after compiling/flattening selectors
Merge pull request #42 from robocoder/filters

Use argument inspection to detect native filter effects
return null to abort builtin
add CSS4 selector tests
@document test per https://developer.mozilla.org/en-US/docs/CSS/@document
parser fixes
apply @nessy patch and add test case
update expected results (this test currently fails)
add test case for multi-extends with nesting (another failing test)
update LICENSE to reflect dual license; add docblock header
add horizontal rules