Added explanation about bundle install with custom Gemfile

 - If tests are to be run against a specific Rails version, all gems
   from the corresponding Gemfile must be installed.
 - This explanation will help new users about how to do bundle install
   with the specific gemfiles.
re-arrange Rakefile - make it still work without bundler/appraisal
re-invent (Java) extension compilation/packaging using "plain" javac/jar
a gem extension for RubyGems to built our extension .jar (WiP)
hack(s) to make the extension compile using installed driver gems
remove (1.3) deprecated files
tune ArJdbc scoped warnings/deprecations
use our deprecate helper instead of warn
handle pre JDBC 4 driver abstract method errors somehow gracefully
use ArJdbc.warn to print warnings from the Java side
probably best to cache strings in a weak map
remove  old (deprecated) jdbc_adapter .rb files
use ArJdbc.warn
minor internal refactoring(s) - move helper method to StringHelper
supress deprecation warnings
print deprecation warning on the deprecated adapter= method
move connection's adapter method into native code
... this also improved readability since @adapter is no longer printed on inspect()
return some more concrete Ruby (native) types
avoid throwing checked exceptions from JRuby methods