slight changes to colors (accent always red) and higher contrast
Several tweaks/refinements.

- Now there is a consistent coloring of the blocks:
  alertblock: always solarized red.
  exampleblock: always cyan.

- block with rounded corners and shadows (e.g. boadilla) thus inherit
  the alert and example block colors. Also the accented color will be
  used for items/enums in the regular block env

- added new example, updated/simplified readme