slack importer: Extract data into directory of zip file.
slack importer: Extract data into directory of zip file.

Currently the zip file is extracted to the root of
zulip directory no matter where the the zip file.
The extracted data is not useful after running the command
which pollutes the zulip directory. It make more sense to
extract it to the same directory of zip file especially
when the zip file gets downloaded to /temp like in the tests.

shubhamdhama/zulip,rishig/zulip,punchagan/zulip,kou/zulip,timabbott/zulip,brainwane/zulip,tommyip/zulip,synicalsyntax/zulip,punchagan/zulip,punchagan/zulip,shubhamdhama/zulip,jackrzhang/zulip,hackerkid/zulip,rht/zulip,hackerkid/zulip,andersk/zulip,kou/zulip,zulip/zulip,synicalsyntax/zulip,showell/zulip,rishig/zulip,eeshangarg/zulip,hackerkid/zulip,timabbott/zulip,shubhamdhama/zulip,andersk/zulip,timabbott/zulip,synicalsyntax/zulip,eeshangarg/zulip,eeshangarg/zulip,shubhamdhama/zulip,eeshangarg/zulip,rht/zulip,brainwane/zulip,punchagan/zulip,shubhamdhama/zulip,timabbott/zulip,brainwane/zulip,zulip/zulip,tommyip/zulip,synicalsyntax/zulip,synicalsyntax/zulip,synicalsyntax/zulip,kou/zulip,dhcrzf/zulip,showell/zulip,showell/zulip,tommyip/zulip,andersk/zulip,showell/zulip,hackerkid/zulip,rishig/zulip,rishig/zulip,brainwane/zulip,jackrzhang/zulip,rishig/zulip,hackerkid/zulip,brainwane/zulip,zulip/zulip,zulip/zulip,zulip/zulip,timabbott/zulip,rht/zulip,punchagan/zulip,kou/zulip,dhcrzf/zulip,zulip/zulip,jackrzhang/zulip,timabbott/zulip,andersk/zulip,rht/zulip,tommyip/zulip,shubhamdhama/zulip,showell/zulip,timabbott/zulip,andersk/zulip,jackrzhang/zulip,jackrzhang/zulip,dhcrzf/zulip,dhcrzf/zulip,rht/zulip,andersk/zulip,kou/zulip,eeshangarg/zulip,synicalsyntax/zulip,rishig/zulip,punchagan/zulip,dhcrzf/zulip,punchagan/zulip,tommyip/zulip,tommyip/zulip,rht/zulip,andersk/zulip,eeshangarg/zulip,shubhamdhama/zulip,showell/zulip,hackerkid/zulip,showell/zulip,tommyip/zulip,brainwane/zulip,jackrzhang/zulip,eeshangarg/zulip,rht/zulip,dhcrzf/zulip,kou/zulip,zulip/zulip,brainwane/zulip,hackerkid/zulip,jackrzhang/zulip,kou/zulip,dhcrzf/zulip,rishig/zulip