add shortcut to access PathItem

to ease the pain to access Operation object
add shortcut to access PathItem

to ease the pain to access Operation object
Merge branch 'fix' of https://github.com/mission-liao/pyswagger into fix
add test case to make sure SwaggerSecurity == SwaggerAuth
clear TODO
add test for patch_obj.py
add test case
add test case
add test case
add test case
add test case
add test case
refine shortcut function
add test case
add test case
add test case
fix
Merge pull request #9 from mission-liao/fix

Fix