Added online_status flag.
Added -D_GNU_SOURCE flag for strdup.
Simplified build instructions.
Added an online/offline indicator in status bar.
Restored build instructions.

This reverts commit 5a99af58d6e7840bfe8f8dc824379a6520e8a257.
Properly fixed cmake install command.
Separated bootstrap process to a function.
Added a return value for tox_weechat_bootstrap.
Added /bootstrap command.