Remove :time key from a record

Prevent time key duplication.
I ran small benchmark.

```rb
require 'benchmark'

n = 10000000
t = Time.now.to_i
h = {'time' => t}

Benchmark.bm do |x|
  x.report { n.times do
      if h.has_key?(:time)
        h.delete(:time)
      end
    end }
  x.report { n.times do
      h.delete(:time)
    end }
end
```

Result:

```
       user     system      total        real
   0.740000   0.000000   0.740000 (  0.736318)
   0.770000   0.000000   0.770000 (  0.772523)
```

`has_key?` is bit faster than `delete`.
Having `:time` key record is very very rare so `has_key?` and `delete` pair is good for this point.