adds ion-hash-test submodule, ensures IonHashTests are performed, upgrades to 'trusty' distribution

[pbcornell]

• adds ion-hash-test submodule
  • updates README.md to describe working with the new submodule
  • removes big-list-of-naughty-strings.txt
  • removes ion_hash_tests.ion
• IonHashTestSuite was not running, addressed by:
  • renaming IonHashTestSuite to IonHashTest
  • renaming IonHashRuner to IonHashTestRunner
• upgrades to 'trusty' distribution

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