propsing a fix for issue #159
fixing a bug in the execution of git rev-list
Optimize bash/zsh checks

Avoid string comparisons. Use instead true/false builtins.
So:
    if [[ $_LP_WORKING_SHELL == bash ]]
becomes:
    if $_LP_SHELL_bash
Optimize _lp_sl/sr/sb
s/if [[ ! -z /if [[ -n /
Merge pull request #168 from dolmen/optimize/sr,sl,sb

Optimize _lp_sr, _lp_sl, _lp_sb
Merge pull request #167 from dolmen/optimize/shell-checks

Optimize bash/zsh checks
Merge pull request #169 from jaesivsm/issue/159

a fix for issue #159
Merge pull request #155 from jaesivsm/fix/git-rev-list

fix for issue #151"bug in _lp_git_branch_color"