Make 'rake build' and 'rake install' work again

This needs require 'bundler/gem_tasks' in Rakefile
Merge pull request #495 from estolfo/bulk-2

Bulk API Update operations
Merge pull request #496 from estolfo/bulk-2

Bulk API deletes
Merge pull request #468 from kkaempf/fix-rake-install

Make 'rake build' and 'rake install' work again
RUBY-787 empty ops and already executed specs