Add instructions to install deps.
modified README.md to help get started with go
Replace lexer with a hand-written one.

Based on Go's bufio.Scanner using a custom Split function and a hack
to pass around token type along with its value.

Three first bytes returned by the scanner are the type, remaining the
value.
Add tests for Lexer.
Rewrite lexer w/o using Go's bufio.Scanner.
Refactor lexing regexp to be more declarative.
Add more lexing rules.
merge master
valid example1.css added and modified grammar