class Crass::TokenScanner

Like {Scanner}, but for tokens!

def collect

execution, and returns them.
Executes the given block, collects all tokens that are consumed during its 
def collect
  start = @pos
  yield
  @tokens[start...@pos] || []
end

def consume

`nil` if there is no next token.
Consumes the next token and returns it, advancing the pointer. Returns 
def consume
  @current = @tokens[@pos]
  @pos += 1 if @current
  @current
end

def initialize(tokens) 

def initialize(tokens)
  @tokens = tokens.to_a
  reset
end

def peek

token.
Returns the next token without consuming it, or `nil` if there is no next 
def peek
  @tokens[@pos]
end

def reconsume

http://www.w3.org/TR/2013/WD-css-syntax-3-20130919/#reconsume-the-current-input-token

Reconsumes the current token, moving the pointer back one position. 
def reconsume
  @pos -= 1 if @pos > 0
end

def reset

Resets the pointer to the first token in the list. 
def reset
  @current = nil
  @pos     = 0
end