[Form] Remove arg from getDefaultOptions()

See: symfony/symfony@b7330456b698f7dd10bd2171c7075fc34c13858e
Merge pull request #43 from Exercise/form-options

[Form] Remove arg from getDefaultOptions()
Fix composer.json - #44
updated Form to 2.1
Merge pull request #46 from jdewit/master

Updated Form to 2.1
Fix PostFormType
Further updates
change: change reference before initial modifications