Set file injector class as parameter (for override)
Allow recursively check uploadable annotation (for inheritance classes)
[doc] Add "Know issues" about file not uploaded when no change on entity

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Related to #123, #8, ...
Update doc

[ci skip]
Merge branch 'gido-patch-1'

Closes #123 #8
Better dependencies definition
Improve travis-ci config
Update mongodb extension
Uses travis composer version
Add php 5.5 to travis build
Merge branch 'master' of https://github.com/c0rrupt/VichUploaderBundle into c0rrupt-master
Fix phpdoc
Minor refactor