Update rspec dependency

[v0dro]

Why is RSpec still at 2.14 in nmatrix? Any specific reason?

I think we should update it to 3.4 (latest).

[wlevine]

Well, we get a ton of warnings about using deprecated RSpec features that will behave differently in RSpec 3. So we would need to change a bunch of tests.

[v0dro]

Is that it?

I think I can do the needful whenever I get some free time.

[lokeshh]

@v0dro Are you on it? If you are not working on this issue let me know. I am interested in doing this.

[v0dro]

Well I'll take some time (~2 weeks). If you're going to do this right away then feel free to do so :)

[lokeshh]

Ok you do it. I will find something else to work upon.

[translunar]

Is there some reason we need the additional features in 3.4? It isn't always beneficial to change a gem dependency. There should be a motivation behind such a change.

[v0dro]

It shows a whole load of deprecation warnings regarding change of syntax.

[v0dro]

Related to #294

[translunar]

Looks like rspec-longrun now supports rspec 3.x, so we can go ahead with upgrading to a newer rspec. :)

https://github.com/mdub/rspec-longrun/issues/5#issuecomment-132267353