compat issue #29: handle old style arguments in objects

New attributes can't be assigned to instancemethods after they've been
declared so add old style function detection to the 'alias' and 'arg'
decorators.
Merge pull request #46 from saaros/master

compat issue #29: handle old style arguments in objects
skip self/cls in the argspec

Instead of get_arg_names, the behaviour of which is non-obvious in the
presence of keyword-only arguments, get_arg_spec is introduced that
returns a modified argspec without self or cls.
add support for keyword-only arguments

Keyword-only arguments are mapped to optional arguments. They are
required iff they have no default value.
fix conflicting option detection with kwonly
Add Travis badge to README
remove python2.7+ syntax
add tests for keyword-only arguments
Merge pull request #53 from Tanriol/feature-kwonly

Keyword-only arguments support (Python3)
Update list of contributors and README
Update year in headers; cleanup setup script
Cleanup setup script
Merge branch 'master' into 47-strict-assembling

Conflicts:
	argh/assembling.py
Normalize hyphen/underscore when comparing a declared arg with function signature
Require an arg to be either positional or optional
Refactor assembling, use OrderedDict