Implement -g (grep) option and abolish -r option

```
teip -g <pattern>
```
=> compatible with grep

```
teip -o -g <pattern>
```
=> only option (current -r option)

```
teip -Oog <pattern>
```
=> Oniguruma + only option (current -R option)

```
teip -g <pattern> -A 3
```
=> compatible with grep -A -B -C