Reload configurations without restarting Emacs
Solution 1:
M-x eval-buffer
Solution 2:
I usually use M-x load-file. But be aware that some initialization is only done the first time through. Things like libraries that set their defaults when loaded, but don't get reloaded the second time through. Its always a good idea to start up emacs from scratch as a final check that everything works ok.
Solution 3:
In the *scratch* buffer, type:
(load-file user-init-file)
Then press C-x C-e to evaluate the expression.