Use #=== operator instead of #match to compare a regexp against a string...

....

It seems that performs better too. I ran this benchmark:

```ruby
require "benchmark/ips"
require "scrivener/validations"

EMAIL = Scrivener::Validations::EMAIL

Benchmark.ips do |x|
  x.report("match") { "frodsan@me.com".match(EMAIL) }
  x.report("===")   { EMAIL === "frodsan@me.com" }
end
```

Results:

```
Calculating -------------------------------------
               match     21712 i/100ms
                 ===     29928 i/100ms
-------------------------------------------------
               match   328645.0 (±6.7%) i/s -    1650112 in   5.046365s
                 ===   534819.5 (±8.7%) i/s -    2663592 in   5.034419s
```

There results are the following: