"charm create" should verify if the given charm name is valid

[amir sanjar]

assuming a charm name starting with a capital character is invalid name ( based on "juju deploy" ) charm create command should return an error.
How to reproduce :

1) >>> :~/charms/trusty$ charm create Sample
...........
..............
>>>:~/charms/trusty$ tree Sample/
Sample/
├── charm-helpers.yaml
├── config.yaml
├── hooks
│   ├── config-changed
│   ├── install
│   ├── start
│   ├── stop
│   └── upgrade-charm
├── icon.svg
├── lib
│   └── charmhelpers
│   ├── core
│   │   ├── fstab.py
│   │   ├── hookenv.py
│   │   ├── host.py
│   │   └── __init__.py
│   └── __init__.py
├── metadata.yaml
├── README.ex
├── revision
├── scripts
│   └── charm_helpers_sync.py
└── tests
    ├── 00-setup
    └── 10-deploy

6 directories, 19 files
sanjar@sanjar-N550JA:~/charms/trusty$ cd ..
sanjar@sanjar-N550JA:~/charms$ juju deploy local:trusty/Sample
error: invalid charm name "local:trusty/Sample"