zsh: simplify shell_code_static
README: add "Support" section
POD: list zsh as a supported shell
README, bin/angel-PS1: more/better doc
fish: kill the angel on exit
bin/angel-PS1: more POD
README: promote fish to first class support
TermTitle: for fish, add an URI to the fish_title doc
Bump $VERSION to 0.94
Travis-CI: test also the zsh engine
README: fix typos
mksh: fix shell_code_static using corpus/special.PS1

spacial.PS1 is now 100% OK.
zsh: fix shell_code_static using corpus/special.PS1

In fact shell_code_static for zsh and mksh are now exactly the same
except for the ps1_finalize call for mksh.
POSIX/dash: do not escape any chars

As the client shell code directly outputs to STDOUT what the angel
produced, we don't need to escape anything.
Now corpus/special.PS1 passes.
ksh: only escape '!' to '!!' in the final result
corpus/special.PS1: also check tabs
mksh, zsh: fix shell_code_static for tabs
zsh: add compatibility with the standard zsh prompt engine

Zsh has already a prompt engine (see 'promptinit'). We now recognize it,
backup it, and disable it. When the angel leaves, we restore the prompt
theme.
bin/: fix shell name detection under cygwin
Shell: minor refactoring