Release 3.0.0-0

• Merge branch 'master' of https://github.com/MartinMalinda/vue-concurrency (59b7a3d)
• Release 2.2.1 (c6589db)
• typo... (#55) (60ad5d5)
• update travis script (479b558)
• add isError method to task group (9c9a377)
• Release 2.1.3 (8105846)
• prevent aborting finished tasks (9d54c45)
• add some progress on effect scope (1f00017)