Remove empty tail segment (1.x branch)

[swankjesse]

Manual backport of cketti's change
https://github.com/square/okio/pull/686/commits

[swankjesse]

Travis config has bitrotted on the 1.x branch. Verified manually.

[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary for Okio (Parent) 1.18.0-SNAPSHOT:
[INFO]
[INFO] Okio (Parent) ...................................... SUCCESS [  1.150 s]
[INFO] Okio ............................................... SUCCESS [02:13 min]
[INFO] Okio Performance Benchmarks ........................ SUCCESS [  1.743 s]
[INFO] Okio Samples ....................................... SUCCESS [  0.337 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------