feat: add fullwidth punctuation to support CJK

[wzru]

I tried to add fullwidth punctuation and now it seems to work well for CJK.
Here is my test code:

package main

import (
	"fmt"

	"gopkg.in/wzru/sentences.v1"
	"gopkg.in/wzru/sentences.v1/data"
)

func main() {
	var text string

	// Compiling language specific data into a binary file can be accomplished
	// by using `make <lang>` and then loading the `json` data:
	b, _ := data.Asset("data/english.json")

	// load the training data
	training, _ := sentences.LoadTraining(b)

	// create the default sentence tokenizer
	tokenizer := sentences.NewSentenceTokenizer(training)

	text = `你好。世界！` //Hello world
	sentences := tokenizer.Tokenize(text)
	for _, s := range sentences {
		fmt.Printf("'%s'\n", s.Text)
	}

	text = `你好吗？我很好。很高兴见到你！`
	// text = `How are you? i'm fine. Nice to meet you!`
	sentences = tokenizer.Tokenize(text)
	for _, s := range sentences {
		fmt.Printf("'%s'\n", s.Text)
	}
}

output:

$ go run main.go
'你好。'
'世界！'
'你好吗？'
'我很好。'
'很高兴见到你！'

[neurosnap]

Thank you for your contribution!