C++11 optimizations

[cdunn2001]

Re: issue #37

[cdunn2001]

E.g. see discussion at pull #75.

Also, with pull #133, we at least have -std=c++0x for gcc and -std=c++11 for clang.

[cdunn2001]

We now have -std=c++11 on master. See #313.

[dan-ryan]

Can we get constexpr added? :)

[cdunn2001]

Sure! Submit a pull-request.

[hjmjohnson]

Support for constexpr now is supported universally, pull requests are welcome.