Unify sanity checks

[Androbin]

Fixes #159
@Matrixcoffee /cc
@non-Jedi /cc

[non-Jedi]

Signoff please and fix following PEP8 issues:

• matrix_client/checks.py:8:1: E302 expected 2 blank lines, found 1
• matrix_client/user.py:3:1: E302 expected 2 blank lines, found 1

[Androbin]

Fixed PEP8, rebased and signed off

[non-Jedi]

LGTM. Appreciate this. :)

[Androbin]

Where else could potentially "dirty" room_id and user_id values be passed?
Should we add this to deprecated client.set_user_id or wait for it's removal?

[non-Jedi]

Not sure where else, and I'm ambivalent on adding it/not adding it to deprecated methods.

[ghost]

Great stuff.

Just one remark: Although room IDs should be fitted with a domain part on creation, those are only informational, and room IDs should be treated as opaque strings anywhere else. Since the domain part isn't actually used by anything, the utility of checking for it seems marginal at best, and it may cause trouble down the road.

[Androbin]

How about an additional defaulted flag?
def check_room_id(room_id, require_domain=False):
We would then pass require_domain=True on creation.

[non-Jedi]

While room IDs may one day be truly opaque and should in general be treated as such by clients, the spec currently says that room ids must have a domain part, so I think leaving the check as-is is reasonable until the spec is changed.