tools/test-all: Split `tools/lint` to match Travis scripts.
tools/test-all: Split `tools/lint` to match Travis scripts.

This keeps `test-all` visibly aligned with `travis/frontend` and
`travis/backend`, which helps us keep it substantively aligned.

showell/zulip,showell/zulip,jackrzhang/zulip,kou/zulip,verma-varsha/zulip,kou/zulip,synicalsyntax/zulip,timabbott/zulip,amanharitsh123/zulip,tommyip/zulip,Galexrt/zulip,eeshangarg/zulip,jackrzhang/zulip,Galexrt/zulip,brockwhittaker/zulip,mahim97/zulip,punchagan/zulip,eeshangarg/zulip,shubhamdhama/zulip,tommyip/zulip,dhcrzf/zulip,brockwhittaker/zulip,showell/zulip,mahim97/zulip,showell/zulip,andersk/zulip,rishig/zulip,kou/zulip,rishig/zulip,amanharitsh123/zulip,punchagan/zulip,andersk/zulip,Galexrt/zulip,zulip/zulip,rht/zulip,brainwane/zulip,hackerkid/zulip,shubhamdhama/zulip,verma-varsha/zulip,hackerkid/zulip,showell/zulip,tommyip/zulip,rht/zulip,shubhamdhama/zulip,zulip/zulip,dhcrzf/zulip,jackrzhang/zulip,brockwhittaker/zulip,synicalsyntax/zulip,zulip/zulip,brainwane/zulip,verma-varsha/zulip,jackrzhang/zulip,amanharitsh123/zulip,rht/zulip,jackrzhang/zulip,brainwane/zulip,rishig/zulip,eeshangarg/zulip,mahim97/zulip,rishig/zulip,synicalsyntax/zulip,rishig/zulip,kou/zulip,punchagan/zulip,amanharitsh123/zulip,kou/zulip,tommyip/zulip,eeshangarg/zulip,mahim97/zulip,synicalsyntax/zulip,andersk/zulip,hackerkid/zulip,brainwane/zulip,zulip/zulip,verma-varsha/zulip,zulip/zulip,synicalsyntax/zulip,andersk/zulip,dhcrzf/zulip,timabbott/zulip,hackerkid/zulip,shubhamdhama/zulip,mahim97/zulip,kou/zulip,brainwane/zulip,andersk/zulip,verma-varsha/zulip,synicalsyntax/zulip,timabbott/zulip,dhcrzf/zulip,mahim97/zulip,timabbott/zulip,timabbott/zulip,synicalsyntax/zulip,showell/zulip,eeshangarg/zulip,Galexrt/zulip,brainwane/zulip,rishig/zulip,hackerkid/zulip,brockwhittaker/zulip,tommyip/zulip,shubhamdhama/zulip,rht/zulip,showell/zulip,rht/zulip,andersk/zulip,timabbott/zulip,brockwhittaker/zulip,brainwane/zulip,shubhamdhama/zulip,zulip/zulip,eeshangarg/zulip,timabbott/zulip,Galexrt/zulip,jackrzhang/zulip,andersk/zulip,punchagan/zulip,zulip/zulip,punchagan/zulip,tommyip/zulip,brockwhittaker/zulip,hackerkid/zulip,amanharitsh123/zulip,rht/zulip,punchagan/zulip,Galexrt/zulip,amanharitsh123/zulip,jackrzhang/zulip,hackerkid/zulip,rht/zulip,dhcrzf/zulip,dhcrzf/zulip,dhcrzf/zulip,punchagan/zulip,eeshangarg/zulip,kou/zulip,verma-varsha/zulip,rishig/zulip,Galexrt/zulip,tommyip/zulip,shubhamdhama/zulip