strip initial `-` from the name of shell process
strip initial `-` from the name of shell process

Avoids the case where shell detection would result in
`basename "-bash"` invocation, triggering the error:

    basename: illegal option -- b

fixes #462

sheerun/rbenv,genome-vendor/pyenv,rbenv/rbenv,dongguangming/pyenv,jmatbastos/rbenv,cehoffman/rbenv,nodenv/nodenv,rridhan/rbenv,jeremy/rbenv,jmatbastos/rbenv,rowhit/pyenv,syndbg/goenv,stivenrgalvis/rbenv,janusnic/rbenv,jrolfs/nodenv,RinSer/rbenv,dark5un/nodenv,ffdc-scm/rbenv-x86_64-linux,SamuraiT/rbenv,Angeldude/rbenv,zmwangx/pyenv,viclim/rbenv,sanemat/rbenv,dnsd/pyenv,blueyed/rbenv,jmatbastos/rbenv,takluyver/pyenv,viclim/rbenv,nebhale/cfenv,intfrr/rbenv,golib/goenv,andrew-christianson/rbenv,cehoffman/nodenv,josegonzalez/rbenv,yyuu/pyenv,jasonkarns/rbenv,peterpih/rbenv,ffdc-scm/rbenv-x86_64-linux,yyyc514/rbenv,sstephenson/rbenv,rbenv/rbenv,docwhat/rbenv,pumpkineater/rbenv,jasonkarns/rbenv,pyenv/pyenv,dongguangming/pyenv,rowhit/pyenv,yeonsh/pyenv,VShangxiao/pyenv,yyyc514/rbenv,mediadoneright/rbenv,cehoffman/nodenv,ox/rbenv,jrolfs/nodenv,SamuraiT/rbenv,sebhahn/pyenv,jeongdeoksu/rbenv,reyesyang/rbenv,fly19890211/pyenv,codesdk/rbenv,yogeshkakde/rbenv,janusnic/rbenv,asaaki/rsenv,recruit-mtl/pyenv,jmatbastos/rbenv,rinrinne/ndkenv,pumpkineater/rbenv,Angeldude/rbenv,josegonzalez/rbenv,rridhan/rbenv,Angeldude/rbenv,cyril/rbenv,jeongdeoksu/rbenv,peterpih/rbenv,peterpih/rbenv,VShangxiao/pyenv,princeofdarkness76/rbenv,jeremy/rbenv,cehoffman/pyenv,bradynpoulsen/rbenv,dnsd/pyenv,lozybean/pyenv,intfrr/rbenv,obimod/pyenv,zmwangx/pyenv,cehoffman/pyenv,andrew-christianson/rbenv,syndbg/goenv,beck/rbenv,yyuu/pyenv,genome-vendor/pyenv,cyril/rbenv,avdhoweb/rbenv,howtolearntocode/rbenv,mediadoneright/rbenv,LawnGnome/rbenv,janusnic/rbenv,UCASREN/pyenv,andrew-christianson/rbenv,lozybean/rbenv,princeofdarkness76/rbenv,docwhat/rbenv,recruit-mtl/pyenv,princeofdarkness76/rbenv,hlecuanda/pyenv,lozybean/rbenv,pumpkineater/rbenv,OiNutter/nodenv,adarshmuthappa/nodenv,cehoffman/rbenv,stivenrgalvis/rbenv,beck/rbenv,ffdc-scm/rbenv-x86_64-linux,jasonkarns/rbenv,rridhan/rbenv,josegonzalez/rbenv,adarshmuthappa/nodenv,stivenrgalvis/rbenv,yyyc514/rbenv,BanzaiMan/pyenv,syndbg/goenv,viclim/rbenv,jmatbastos/rbenv,fly19890211/pyenv,Ferocia/rbenv,avdhoweb/rbenv,dark5un/nodenv,jmatbastos/rbenv,jf/rbenv,avdhoweb/rbenv,xshwy/pyenv,habinmusic/pyenv,howtolearntocode/rbenv,UCASREN/pyenv,ffdc-scm/rbenv-x86_64-linux,reyesyang/rbenv,intfrr/rbenv,jmatbastos/rbenv,hlecuanda/pyenv,docwhat/rbenv,nodenv/nodenv,peterhoeg/rbenv,sstephenson/rbenv,pyenv/pyenv,codesdk/rbenv,michael-gabenna/rbenv,yogeshkakde/rbenv,Ferocia/rbenv,mediadoneright/rbenv,bradynpoulsen/rbenv,reyesyang/rbenv,pyenv/pyenv,OiNutter/nodenv,yeonsh/pyenv,lozybean/rbenv,BanzaiMan/pyenv,cehoffman/luaenv,cehoffman/luaenv,michael-gabenna/rbenv,bradynpoulsen/rbenv,cyril/rbenv,codesdk/rbenv,howtolearntocode/rbenv,takluyver/pyenv,jeremy/rbenv,xshwy/pyenv,sstephenson/rbenv,sebhahn/pyenv,SamuraiT/rbenv,chenfengyuan/pyenv,lozybean/pyenv,chenfengyuan/pyenv,sebhahn/pyenv,syndbg/goenv,RinSer/rbenv,ffdc-scm/rbenv-x86_64-linux,cehoffman/rbenv,obimod/pyenv,beck/rbenv,RinSer/rbenv,habinmusic/pyenv,michael-gabenna/rbenv,yogeshkakde/rbenv,jeongdeoksu/rbenv,Ferocia/rbenv