Fix some reflection warnings

> Reflection warning, liberator/util.clj:35:3 - call to java.util.Date ctor can't be resolved.
> Reflection warning, liberator/util.clj:38:16 - call to method format can't be resolved (target class is unknown).
> Reflection warning, liberator/util.clj:44:7 - call to method parse can't be resolved (target class is unknown).
> Reflection warning, liberator/representation.clj:183:25 - call to method equalsIgnoreCase can't be resolved (target class is unknown).
> Reflection warning, liberator/representation.clj:185:6 - call to method getBytes can't be resolved (target class is unknown).
> Reflection warning, liberator/core.clj:230:56 - reference to field toString can't be resolved.
> Reflection warning, liberator/core.clj:339:27 - call to method after can't be resolved (target class is unknown).
> Reflection warning, liberator/core.clj:376:13 - call to method after can't be resolved (target class is unknown).
> Reflection warning, liberator/dev.clj:25:27 - call to method endsWith can't be resolved (target class is unknown).
> Reflection warning, liberator/dev.clj:30:43 - reference to field getTime can't be resolved.