Add __version__ and __file__ variable

[jpatacz]

version and file variable will add some more information about the package within the code.

[jpatacz]

@flskillcorner do you think such version documentation would be good (class attribute):

from skillcorner.client import SkillcornerClient
SkillcornerClient.__version__
'1.0.2'
skc_client = SkillcornerClient('username', 'password')
skc_client.__version__
'1.0.2'

or would it be better to do it this way (package attribute):

import skillcorner
skillcorner.__version__
'1.0.2'

[flskillcorner]

@jpatacz
On public modules, I have essentially saw the second option (skillcorner.version), so I prefer we do the same thing

[jpatacz]

And what about file variable ?

[flskillcorner]

What I saw for file : each import of module should have a file attribute, but not object attached to module, neither instances
Example :
`In [65]: from django.core.serializers import xml_serializer

In [66]: xml_serializer.file
Out[66]: '/home/franck/envi/base37/lib/python3.7/site-packages/django/core/serializers/xml_serializer.py'

In [67]: from django.core.serializers.xml_serializer import settings

In [68]: settings.file

AttributeError Traceback (most recent call last)
in
----> 1 settings.file

~/envi/base37/lib/python3.7/site-packages/django/conf/init.py in getattr(self, name)
78 if self._wrapped is empty:
79 self._setup(name)
---> 80 val = getattr(self._wrapped, name)
81 self.dict[name] = val
82 return val

AttributeError: 'Settings' object has no attribute 'file'`