v0.2.0: add quick start to README (#82)

* add quick start to README

The vast majority of users probably just want `@btime`, so I think it is useful to include a "quick start" section in the manual that just gives a couple of examples (including interpolation).

* global -> external, add links

* move quick start after documentation section

v0.1.0

Fix depwarns under 0.7 that do not break 0.6, and bump REQUIRE and CI…

v0.0.8

Load BenchmarkTools when loading a params.jld file (#54)