Fixes curl install with space in custom install path

[derekbekoe]

Instead of using command.split(), pass in the command to execute as a list always

See #1070

virtualenv and pip don't work well with spaces in paths though so installs with spaces will still fail until that's addressed:
pypa/virtualenv#53
pypa/pip#923

[tjprescott]

You could also look into the shlex module, which will let you split but preserve spaces in quoted strings.

[derekbekoe]

@tjprescott I tried it but it behaved in the same way:

import shlex
dir = '/users/myname/Documents/Virtual Machines/share/software/azure'
txt = '{0} virtualenv.py --python {0} {1}'.format('/usr/bin/python', dir)
shlex.split(txt)
txt.split()