##### SUMMARY
`ansible-galaxy collection install` currently requires the user to specify an install path using the `-p` option. Galaxy currently generates and displays the CLI command for installing a collection. There is no way for Galaxy to determine a value for `-p`, and hard coding a default value into Galaxy makes no sense.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
`ansible-galaxy`

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```
ansible 2.10.0.dev0
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/Users/chouseknecht/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/chouseknecht/projects/ansible/lib/ansible
  executable location = /Users/chouseknecht/.pyenv/versions/venv27/bin/ansible
  python version = 2.7.14 (default, Nov 14 2017, 23:24:24) [GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.38)]
```

else:
            
            
            for rname in context.CLIARGS['args']:
                role = RoleRequirement.role_yaml_parse(rname.strip())
                roles_left.append(GalaxyRole(self.galaxy, self.api, **role))
        for role in roles_left:
            
            if role_file and context.CLIARGS['args'] and role.name not in context.CLIARGS['args']:
                display.vvv('Skipping role %s' % role.name)
                continue
            display.vvv('Processing role %s ' % role.name)
            
            if role.install_info is not None:
                if role.install_info['version'] != role.version or force:
                    if force:
                        display.display('- changing role %s from %s to %s' %
                                        (role.name, role.install_info['version'], role.version or "unspecified"))
                        role.remove()
                    else:
                        display.warning('- %s (%s) is already installed - use --force to change version to %s' %
                                        (role.name, role.install_info['version'], role.version or "unspecified"))
                        continue
                else:
                    if not force:
                        display.display('- %s is already installed, skipping.' % str(role))
                        continue
            try:
                installed = role.install()
            except AnsibleError as e: