rename value to camel case
#389 Added draft of exceptions handler
remove unused import
Style refactoring: Methods which contain a single match expression should be declared in single line

http://docs.scala-lang.org/style/declarations.html#methods
Small refactor: collapse code

No sence using following code, because we are inside FieldConversions
and has asList method for Fields class.
val ids: Seq[Comparable[_]] = (0 until fields.size).map { fields.get(_)
}
Format edges initialization.
Small refactoring

No sense using "(0 until actual.size).foreach { i => actual.get(i) ..."
we has "asList" method.
#389 Write test for handling exceptions using XHandler
Remove return keywork
#389 Tool surround with try catch using draft of the XHandler.

https://github.com/twitter/scalding/issues/389
Rename params.
Rename key argument with prefix k.
Merge pull request #400 from lashchenko/AL

Al