preserve status/body on failed http-requests

refs #149
test for #140
PSR-4 + Namespaces
updated dependencies
convert test-helper classes to PHP-5.3+ style
tweak class-names in strings
converted HTTP unit-tests to use namespaces
proper registration of literal-classes
namespaced classes for Format, TypeMapper
Converted Literal unit-tests to use namespaces
merged EasyRdf\Http\Exception