Remove extra semicolon in Task.scala

Author: GuoQiang Li <witgo@qq.com>

Closes #1876 from witgo/remove_semicolon_in_Task_scala and squashes the following commits:

c6ea732 [GuoQiang Li] Remove extra semicolon in Task.scala
Merge remote-tracking branch 'upstream/master' into Word2Vec-improve
use PrimitiveKeyOpenHashMap to represent model