Fixed operator precedence

Placed all operators inside the `expr` rule to get the expected operator precedence.

Changed:

    expr
     : ...
     | expr binop expr
     | ...
     ;

    binop
     : '+' | '-' | AND | OR | ...
     ;

to

    expr
     : ...
     | expr ('+' | '-') expr
     | expr AND expr
     | expr OR expr
     | ...
     ;
SCSS Grammar and tests
Merge pull request #47 from bkiers/patch-1

Fixed operator precedence
test includes, imports, mixins and fixing grammar with params
Added an ECMAScript grammar.
Update README.md
Update README.md
Update README.md
Merge pull request #48 from bkiers/ecmascript

ECMAScript grammar
scss function test
nested functions
conditionals
while and for conditional tests
first commit fast
little more cunning
readme
removing args thing
removed double paren
SCSS Parser complete v1
added BSD license