Fixes #128

We should wait till travis passes.

Here's one of my commit messages, copied for convenience:
```
In travis, use the -Werror flag, as advised by @scpeters. Doing so
required me to improve how I add the -std=c++11 flag to CMAKE_CXX_FLAGS.

In the future, the way I set CMAKE_CXX_FLAGS should maybe conform to how
@sherm1 has done it, with a separate BUILD_CXX_FLAGS variable.
```

By the way, I used cherry-pick here to get @sherm1's nlpqlp fix so that travis
might pass. My first time using cherry-pick!