Improve Multiple_cursors_before and Multiple_cursors_after examples

Add check for existence of :NeoCompleteLock and :NeoCompleteUnlock prior to trying to exec them. This is needed in the case of delayed activation of neocomplete (e.g. with NeoBundleLazy).
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Merge pull request #5 from MadAnd/patch-1

Improve Multiple_cursors_before and Multiple_cursors_after examples