Add .travis.yml

Do Travis CI testing with clang and gcc, on 64-bit Ubuntu Trusty.
Performance would probably be better using the container-based Travis
infrastructure, but that is currently limited to Precise, and we would
need some important apt packages whitelisted, e.g., dejagnu.

(cherry picked from commit 09e8307da049cf90bb1f7b9b4b1608a0b9130fd9)

https://github.com/krb5/krb5/commit/6d740fb6e8f14e4592f98455206ad0653e46f079
Author: Tom Yu <tlyu@mit.edu>
Commit: 6d740fb6e8f14e4592f98455206ad0653e46f079
Branch: krb5-1.13
 .travis.yml |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)