Renamed tests.jl to runtests.jl

To comply with the new standard in
https://github.com/JuliaLang/julia/pull/6191
Merge pull request #34 from JuliaLang/rename

Renamed tests.jl to runtests.jl
fix Travis config
Update README.md
Update api.md

Add warning that this discusses a future API. Close #35
Generalize oderkf to support orders != 5. Add ode23_bs based on oderkf.
Add performance comparison for adaptive solvers.
Some cosmetics & new test added (B5).
Devectorization in oderkf, oderosenbrock and ode_ms (fixes problems related to JuliaLang/julia#6118).
Cleaned up performance test.
Added backward propagation in oderkf (part of #2).
Remove performance test for now.