make function calls with enum arguments JustWork

matches behavior of JRuby FFI
make function calls with float arguments JustWork with enums
pass options to rspec call
Add specs for non int enum arguments

not all pass currently
additional specs and a minor fix
Add optional FFI::Type argument to Library#enum and Enum.new

alll tests pass
documentation
add jruby to tests

also gitignore .bundle and vendor
this is largely to cause travis to rerun the tests
re-add EnumTest additions
Merge pull request #321 from tduehr/typed_enums

Typed enums