Remove FlashMessenger view helper

[weierophinney]

Remove FlashMessenger view helper as requested by zendframework/zend-mvc-plugin-flashmessenger#3

Complementary port to MVC Plugin PR is at zendframework/zend-mvc-plugin-flashmessenger#10

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Originally posted by @alextech at zendframework/zend-view#95

[weierophinney]

needs rebase

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Originally posted by @samsonasik at zendframework/zend-view#95 (comment)

[samsonasik]

I created PR #47 for it.