- fixed a description of spark.mesos.executor.memoryOverhead from 7% to 10%
- This is a second part of SPARK-6085

Author: Jongyoul Lee <jongyoul@gmail.com>

Closes #5065 from jongyoul/SPARK-6085-1 and squashes the following commits:

c5af84c [Jongyoul Lee] SPARK-6085 Part. 2 Increase default value for memory overhead - Changed "MiB" to "MB"
dbac1c0 [Jongyoul Lee] SPARK-6085 Part. 2 Increase default value for memory overhead - fixed a description of spark.mesos.executor.memoryOverhead from 7% to 10%