DateElement now support a string
fixed a typo on classname
added tests
proper solution of handling exceptions in tests
Fixed CS issues
Merge branch 'hotfix/form-datetime' of git://github.com/macnibblet/zf2 into hotfix/3276
[#3276] import DateTime as PhpDateTime to avoid ambiguity
Merge branch 'hotfix/3276' into develop

Close #3276