updated copyright
cleaned up some package dependency stuff
minor cleanup
enabled which-func in all modes that support it
added flycheck-mode
fixed a typo
disable flycheck until issues with package installation are resolved upstream
flycheck issue with package.el is now resolved upstream
enable whitespace-mode in modes derived from text-mode
added contribution guidelines
removed the mention of prelude-modules from the README
Add ace-jump-mode to the default package set.
Move Prelude's menu item under Tools.
Add imenu support for markdown-mode.
Fix the toggle behavior of prelude-mode.
Make the list of modules loaded by Prelude configurable.

Modules loaded by Prelude can now easily be adjusted via
the file `prelude-modules.el` in Prelude's installation folder.
To disable a module simply comment it out; conversely uncomment
a module to enable it.
Auto-install slim-mode.
Map Command to Meta as well.
Remove dubious workaround for package.el timeout problem.
Fix #255.

`prelude-duplicate-current-line-or-region` was broken after the introduction of
dash.el.