Discrete Problems

Add the @muladd macro, and discrete problems.

Enhanced Interpolations and inplace noise

v0.8.0

enhanced interpolations for all!

Callback interface change and plot labels are better

Small changes. The plot changes are silent but will make the plots look nicer.
The callback changes a keyword arg to a different constructor, and for now throws
a depwarn if you try to use the old kwarg. Lastly, the integrator interface
was slightly expanded in terms of the cache iterators.

Add DDEs and New Callbacks

Delay Differential Equations were added, and the callbacks were split to DiscreteCallback and ContinuousCallback types.

Integrator and Callback Interfaces, Delay Equations

This is an exciting update which adds the integrator and callback interfaces to the common interface. Also included are types for differential delay equations to make way for DelayDiffEq.jl. While they may go under further refinement, most of those changes should be increasing the amount of methods available.

Breaking changes include a change from tab to tableau for the tableaus, which breaks usage in OrdinaryDiffEq's ExplicitRK (not bound because it's mostly a test tool) and DiffEqDevTools tableaus. Also, ParameterizedFunction was renamed to AbstractParameterizedFunction so that ParameterizedFunctions.jl could have a concrete ParameterizedFunction type which takes in user defined functions (non-macro based form which works with the parameter estimation suite).

Also included are minor updates to plot recipes and typing on test problems.