Enable passing custom arguments to tmux

Custom arguments can now be passed to tmux by setting the
TMUXIFIER_TMUX_OPTS environment variable.
Bump version to 0.9.0
Fixing the export path option for bash and zsh in the README
Add /home/wikimatze variable
Merge pull request #29 from matthias-guenther/installation-fix-for-zsh

Problems with zsh installation
Add completion for fish shell
Merge pull request #31 from trekdemo/fish_completion

Add completion for fish shell
Fix issue #28, default-path error with Tmux 1.9

When using Tmux 1.9 and later the "-c" argument is given to the
"new-session" command to set the session's root/default path. When using
Tmux 1.8.x and earlier, the old "default-path" session option method is
used instead.
Bump version to 0.9.1
Initialization under fish
Update README with fish related stuff
Merge pull request #32 from trekdemo/fish_support

Full fish shell support
Update copyright year
Mention fish shell where sensible
Improve Update section, slightly, just slightly :)
Improve TMUXIFIER_TMUX_OPTS section
Bump version to 0.9.2
Bump version to 0.10.0

The 0.9.2 bump should have been 0.10.0. Support for fish shell was
added, hence a minor version bump is needed, not a patch.
Improve custom tmux arguments section

Don't ask why there was no header, cause it's beyond me >_<
Fix typo in code comment