README: add AUTHORS section with coderwall.com links
Fix typo in README.md
Handle neagative temperature in _lp_acpi_temp
_lp_temp_acpi: simplify regexp
_lp_temp_acpi: guard against any future l10n of 'acpi'
implementing issue #110

as the activation of GIT_PS1_SHOWUPSTREAM option does for __git_ps1
the _lp_git_branch_color now compute how many commit we are ahead or
behind of our remote reference.