0.5.3 Bugfix and maintenance release

Release 0.5.3 includes various bug fixes (see changelog) and one breaking but likely low impact change: BREAKING: 0.5.3 changes behavour of builder create calls so arguments are always ordered by field id when id attributes are being used, for example MyGame_Example_Monster_create() in monster_test.fbs (#81). Fixes undefined behavior when sorting tables by a numeric key field.