Change oldest supported Racket version to 5.3.2
Merge branch 'qerub-if&when-not'

By Christoffer Sawicki (2) and Greg Hendershott (1)
* qerub-if&when-not:
  Add {if,when}-not
  Test {if,when}-let by checking macroexpanded code
  Set `current-namespace` to make test work with Racket 5.3.2

https://github.com/greghendershott/rackjure/pull/12
Closes #12.

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