Fix shell detection for login shells

Login shell may have a command name in the process table starting with a
'-'. This is the case in particular on Mac OS X.
We now remove that '-' in the shell detection code.
Closes #5. Thanks to @LudovicRousseau for the report.
Travis-CI: add notifications to the IRC channel
Travis-CI: don't show the commit info (Github will do it)
examples/2lines.PS1: use WorkingDir_Tilde
Travis-CI: improve IRC notification message
Travis-CI: fix IRC notification message
bash: cleanup APS1_PROMPT_COMMAND
bash: uninstall the EXIT trap on leave
POSIX shell: in EXIT trap, check if the angel function exists
Travis-CI: do more tests on perl 5.8

Our builder (the 'dist' script) is made for perl 5.10, so we can not run
it under perl 5.8 on Travis-CI, so many tests fails.
So we won't use the builder and its result unless we are on perl 5.10+
and we will test the other things using "perl -Ilib bin/angel-PS1".
The built script is tested by Travis-CI on the 'release' branch anyway.
Travis-CI: skip building the fatpacked script if perl 5.8
Travis-CI: fix YAML
Travis-CI: fix YAML (2)
VCS plugin: fix _find_vcs_dir

It was not working at all unless if the repo was the current directory
VCS plugin: fix issue when out of any VCS controlled dir
Travis-CI: improve IRC notification message
README: fix layout
README: updates
Full zsh support!

The shell_code_static was hard!
README: document zsh support