Transition changes in 2.1.7

[StarpTech]

Hi, this change can influence all your components.

vue-bulma/modal#6

[fundon]

Thank you.

BTW, welcome PR.

[luventa]

@StarpTech According to the issue I raised, we will skip over vue 2.1.7 to avoid this transition issue.
Thanks.

[fundon]

Vue updates to v2.1.8. Landed in 6d7ad76.