added import-java-ns. This approach needs to locate the class in the
imported packages and this is only possible in runtime, so I need to rewrite
mangle-class-name and expand-type to be regular procedures instead of
expansiontime macros.
Update README.md
Handle class/method/field not found

- added class/or-error variant which raises an error if the class
  doesn't exists
- jlambda-method, jlambda-constructor and jlambda-field raises error if
  method, constructor or field doesnt exists.. ON DEFINITION
- added jlambda-method* variant, which avoid checking until execution,
  useful for library provided methods
Merge branch 'jimport-java-ns' of github.com:chicken-mobile/jni into jimport-java-ns
Merge pull request #2 from chicken-mobile/jimport-java-ns

Jimport java ns