REF: install asv in the profiled environment

[jbrockmendel]

Having asv install itself in the profiled environment would open up a lot of options. In particular, I think it would be necessary for something like #482 to be implemented.

I'd like to poke at this and see what it makes possible, but my first couple attempts at injecting asv into the environment failed. @pv is there an easy way to do this?

[HaoZeke]

Not required anymore. asv_runner is installed per environment, and includes decorators.