Support `source ~/.bashrc` when installing

When you first install thefuck, you get this nice message.

$ fuck
Seems like fuck alias isn't configured!
Please put eval "$(thefuck --alias)" in your ~/.bashrc and apply changes with source ~/.bashrc or restart your shell.
Or run fuck second time for configuring it automatically.
More details - https://github.com/nvbn/thefuck#manual-installation

$ fuck
fuck alias configured successfully!
For applying changes run source ~/.bashrc or restart your shell.

Which is great and I love it, however, when I run fuck again, I get the same message.

$ fuck
fuck alias configured successfully!
For applying changes run source ~/.bashrc or restart your shell.

Seems like an oversight. It should suggest running source ~/.bashrc.