TEZ-1836. Provide better error messages when tez.runtime.io.sort.mb,
spill percentage is incorrectly configured. Contributed by Vasanth kumar
RJ.
(cherry picked from commit 665801c6d4d3721d2b6d82df3a2e009548e209c3)
Fixed 0.5.4 section in CHANGES.txt
Set release date for 0.5.3 release.
(cherry picked from commit 5bdc78872c749200ea7e2895a08c7c43ff845f54)
TEZ-1861. Fix failing test: TestOnFileSortedOutput. (sseth)
(cherry picked from commit e8d7dc9dc1463d5bb0e36144b0e9d0f9bab599ac)

Conflicts:
	CHANGES.txt