[travis] option to run valgrind in travis.
[travis] Testing valgrind output

[ci valgrind]
[travis] Fix bash bug; install valgrind.
[travis] Try running valgrind

[ci valgrind]
[travis] Make valgrind check less error-prone.
[travis] Run valgrind.

[ci valgrind]
[travis] bash syntax
Update .travis.yml
[travis] test building valgrind

[ci valgrind]
[travis] Don't run valgrind this time.
Fix merge conflicts.
Merge pull request #175 from chrisdembia/travis-valgrind

Allows developers to tell travis to run valgrind with ctest