v0.8.0

News:

• [breaking] stepplot, lsimplot, impulseplot now have the same signatures as their corresponding non-plotting functions.
• New function d2c (inverse of c2d).
• New method :fwdeuler for c2d (and d2c).
• Styles of plots will now use the current default theme set in Plots instead of a custom style.
• The controller function in lsim can now return a scalar if the system has a single input.
• Bugfixes