Fix backend accept types

Fix accept file types

Bugfix release

Fixing issue relative to files not correctly renamed.

See #9

Widening allowed version for session manager dependencies

v1.2.3

Widening session manager dependencies

fixing issue (missing json_encode() for custom error messages)

Merge pull request #8 from nguyenk/master

fix issue

Bugs fixes on fileSize validation & custom error messages

Merge pull request #7 from nguyenk/master

allow custom error messages & fix bugs : min / max fileSize were not tested