Fix #167, #202, #204, #274 and a bunch of other goodies

[HaleTom]

@ghthor and @nathanb could I have your feedback on this PR? Also, please tag anyone else you believe should review this PR.

Fixes

• Fix #167: "Empty string arguments not being passed to git"
• Fix #202: "Wrong argument quoting when filename uses spaces"
• Fix #204: "File names with shell-special characters"
• Fix #274: "$e# variables are set incorrectly with ll dir1 dir2"

What's in the can:

• Return (well, print actually) a quoted array from scmb_expand_args() via declare -p. This array can then be reconstituted in the caller by eval "args=$(scmb_expand_args "$@")".
• Add _safe_eval(): quote $@ elements before eval to prevent, eg, eval "echo" "foo;date" from running date. With _safe_eval, the output will be foo;date.
  • Add _token_quote test helper which prints the shell-escaped version of each of its arguments.
• Don't clobber user's $IFS: use locally scoped $IFS variables.
• Replace all instances of unquoted $@ with "$@" to prevent splitting of array elements by $IFS
  • Likewise, replace ${array[@]} with "${array[@]}"
• Invoke readlink -f in a way which can succeed
• Loosen regex match in strip_colors() to pass tests
  • Tests will otherwise fail with $LS_COLOURS as set by https://github.com/trapd00r/LS_COLORS
• assert(Not)?Includes: call _includes with an array
• test_helper.sh: Don't clobber global name/email config
• shell_shortcuts_test.sh: correct quoting
• scmb_expand_args(): return an array to fix quoting issues
• _print_path: remove unnecessary pipeline
• test_ls_with_file_shortcuts(): clean up temp files after use
• ls_with_file_shortcuts(): print error to STDERR
• Allow run_tests.sh to be executed from anywhere
• Ensure file ordering matches in both ls invocations in ls_with_file_shortcuts
• git_show_affected_files: make $f local

May fix #183: "Breaks cd when using other languages" (awaiting reproduction instructions)

May contain traces of peanuts. Reviews gratefully received.

[HaleTom]

Oops, I just read that it's a bad idea to git push with -f to a PR branch.

I did it at 2018-09-02 05:30 UTC if it helps to de-fuxor things at your end.

[HaleTom]

Awaiting "Upgrade Travis CI environment to newer versions of bash and zsh #264" to proceed.

[nathanb]

@HaleTom Thanks for the include, but I think you might be referring to @ndbroadbent instead.

[ghthor]

This PR is shaping up really nicely! I need to fix that Travis_CI build #264

[HaleTom]

This is finally green with Travis.

Can I please get a LGTM or two?

[ghthor]

@HaleTom @jeffbyrnes Any more reservations? Can I get a LGTM for my conflict resolution in a8cf407?