Unset RUBY_VERSION_FILE when loading auto.sh

Ensure that chruby will be called or reseted after auto.sh is loaded.
This fixes a problem when for example a new tmux window is opened and
environment variables (including RUBY_*) reserved, but PATH is reset in
.zshrc/.bashrc. The root cause is thus same than in #46.
Fixed the Arch Linux Install example (@maxmeyer).
Fix test runner's exit code if any test fail
Merge pull request #86 from tmatilai/test-runner-exit-code

Fix test runner's exit code if any test fail
Merge pull request #83 from tmatilai/unset-version-file

Unset RUBY_VERSION_FILE when loading auto.sh
Unset RUBY_VERSION_FILE at the top.
Drop shebangs from bug_report and test scripts

At least `[[ ]]` and arrays are not Posix shell compatible.
And anyway it is better to run the scripts by default using
the current SHELL.

The only exception is `test/runner` that uses bash by default,
as it is normally used via make that uses /bin/sh otherwise.
Fix RUBY_ROOT in bug_report.sh
Fix auto-switching tests

The correct variable is RUBY_ROOT, not RUBY. It seemed to be renamed
during the development of auto-switching functionality.
Merge pull request #87 from tmatilai/bug_report

Fix RUBY_ROOT in bug_report.sh
Merge pull request #88 from tmatilai/fix-auto-tests

Fix auto-switching tests
Merge pull request #84 from tmatilai/non-posix-sh

Use bash in scripts and tests
If $PS1 isn't set, re-run the $SHELL in interactive/login mode.
updated Ruby version from 1.9.3-p374 to p385
Merge pull request #91 from havenwood/patch-6

updated Ruby version from 1.9.3-p374 to p385
Version bump to 0.3.3.
Invoke ruby using the fully qualified path to avoid aliases.
Fix typo.
Silence stderr of which.
Added a description.