Update Truth version to 0.18.

This version includes primitive type arrays, improved String support, renaming of the object under test, as well as custom error messages.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=67639126
Release FutureCallbackTest to Guava.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=67707789
Test that it's possible to attach a callback to a ListenableFuture<?>.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=67713851
Shuffling from internal change.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=67842017
Fix overflow issues in LocalCache, as per Guava issue 1761
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68007129
Expand Javadoc of Multimap to clarify unusual hashCode implementations, as per Guava issue 1722.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68093584
java/com/google/common: CL generated with data from dead-code analysis
using //devtools/scythe:remove_dead_code
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68103937
Increase the symmetry of the Javadoc changes to Multimap.hashCode().
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68397956
Widen Multisets.removeOccurrences to accept Iterables.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68409485
Add "et" as an effective TLD.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68415393
Shuffling from internal-only change.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68416232
Add default instances of ByteSource, ByteSink, CharSource and CharSink to ArbitraryInstances. (Guava issue 1770.)
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68417594
Updating comments to fix statements that MoreExecutors.sameThreadExecutor is used if an Executor is not supplied, which is no longer actually the case since we switched the defaults to the internal INLINE_EXECUTOR.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68506380
Shuffling from internal-only change.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68641973
Fix EventBus to not include bridge methods when registering subscribers under Java 8. Annotations are included on bridge methods in Java 8 where they weren't before.

(Guava issue 1549.)
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68654467
Make ImmutableCollection.Builder public in the GWT emulation.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68729337
Add a benchmark for [Google-internal -- this CL will be rolled back in Guava] isPrime on positive inputs.  The input distribution is logarithmic.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68733770
Add application/x-protobuf.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68866844
Shuffling from internal-only change.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=69004612
Strip isPrime benchmarks from Guava, since isPrime itself is @GoogleInternal.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=69012929