Use bash builtins for reading user input.
Use bash builtins for reading user input.

PHP's readline extension doesn't implement all the features from the
native GNU readline library, such as Ctrl+u.

Plus, a large percentage of PHP installs probably don't even have `--with-readline` enabled.

The method used in this commit was inspired by wpshell.

see #89

borekb/wp-cli,duncanjbrown/wp-cli,boonebgorges/wp-cli,spiritedmedia/wp-cli,blueblazeassociates/wp-cli,gitlost/wp-cli,xwp/wp-cli,a7127cff69cab32e5c4723e8446e21c4b7325dc/wp-cli,macbookandrew/wp-cli,aaemnnosttv/wp-cli,rohmann/wp-cli,a7127cff69cab32e5c4723e8446e21c4b7325dc/wp-cli,blueblazeassociates/wp-cli,aaemnnosttv/wp-cli,heiglandreas/wp-cli,gedex/wp-cli,staylor/wp-cli,spiritedmedia/wp-cli,blueblazeassociates/wp-cli,staylor/wp-cli,Yas3r/wp-cli,miya0001/wp-cli,rodrigoprimo/wp-cli,duncanjbrown/wp-cli,miya0001/wp-cli,nyordanov/wp-cli,GaryJones/wp-cli,trepmal/wp-cli,shawnhooper/wp-cli,anttiviljami/wp-cli,boonebgorges/wp-cli,macbookandrew/wp-cli,JohnDittmar/wp-cli,trepmal/wp-cli,xwp/wp-cli,JohnDittmar/wp-cli,nyordanov/wp-cli,boonebgorges/wp-cli,ahmadawais/wp-cli,2ndkauboy/wp-cli,rohmann/wp-cli,gedex/wp-cli,shawnhooper/wp-cli,miya0001/wp-cli,shawnhooper/wp-cli,rodrigoprimo/wp-cli,Yas3r/wp-cli,gedex/wp-cli,staylor/wp-cli,trepmal/wp-cli,nyordanov/wp-cli,anttiviljami/wp-cli,GaryJones/wp-cli,rodrigoprimo/wp-cli,GaryJones/wp-cli,2ndkauboy/wp-cli,Yas3r/wp-cli,borekb/wp-cli,anttiviljami/wp-cli,duncanjbrown/wp-cli,rmccue/wp-cli,borekb/wp-cli,here/wp-cli,macbookandrew/wp-cli,JohnDittmar/wp-cli,dpq/wp-cli,ahmadawais/wp-cli,ahmadawais/wp-cli,spiritedmedia/wp-cli,here/wp-cli,pressednet/wp-cli,dpq/wp-cli,gitlost/wp-cli,gitlost/wp-cli,pressednet/wp-cli,2ndkauboy/wp-cli,rohmann/wp-cli,a7127cff69cab32e5c4723e8446e21c4b7325dc/wp-cli,dpq/wp-cli,pressednet/wp-cli,xwp/wp-cli,heiglandreas/wp-cli,aaemnnosttv/wp-cli,rmccue/wp-cli