fixes #4: support ObjectExpression properties without a `type` member
generalised wrapper solution to simplify similar future problems

as requested by @jasvir at https://github.com/Constellation/estraverse/commit/80d3e6b42f4eb4a4db9b9897895729ef20b65a80#commitcomment-2404694
fixes #4 for `replace`

see also 80d3e6b42f4eb4a4db9b9897895729ef20b65a80 and 47c00b774ce5385de2da09a1ca164ae32fbd47ee
Merge pull request #5 from michaelficarra/GH-4

support ObjectExpression properties without a `type` member