exp/html: simplify some of the parser's internal methods.
exp/html: simplify some of the parser's internal methods.

benchmark          old ns/op    new ns/op    delta
BenchmarkParser      4006888      3950604   -1.40%

R=r, andybalholm
CC=golang-dev
http://codereview.appspot.com/6301070

dsriram/golang,pombredanne/go-deleteme,pombredanne/go-deleteme,dsriram/golang,pombredanne/go-deleteme,tv42/old-go,dsriram/golang,gnanderson/go,dsriram/golang,dsriram/golang,pombredanne/go-deleteme,tv42/old-go,apparentlymart/golang,apparentlymart/golang,gnanderson/go,apparentlymart/golang,pombredanne/go-deleteme,apparentlymart/golang,gnanderson/go,tv42/old-go,apparentlymart/golang,tv42/old-go,pombredanne/go-deleteme,dsriram/golang,gnanderson/go,apparentlymart/golang,tv42/old-go,dsriram/golang,gnanderson/go,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,gnanderson/go,gnanderson/go,apparentlymart/golang