中文

Fix

• Fix(Same File Path): Avoid two tasks writing to the same file simultaneously, Once there is an another running task with the same target path to the current task's, the current task will receive the PathConflictException to refused start downloading. Closes #471

New Interfaces

• Add FileDownloadSerialQueue#getWaitingTaskCount: Get the count of tasks which is waiting on the serial-queue instance. Refs #345