Added @FileExists validation annotation to Sumac
Incorporated feedback, Added support for File type
Merge branch 'master' into karthik/file-exists-validation

Conflicts:
	core/src/test/scala/com/quantifind/sumac/ValidationSuite.scala
Merge pull request #31 from quantifind/karthik/file-exists-validation

Added @FileExists validation annotation to Sumac