update naming

rename
- app.schema -> app.root
- app.rs -> removed
- app.m -> app.d
- obj.py -> objects.py

add:
- app.pd: Parameter Definition
- app.rd: Response Definition
local scope separator
add parser & objects for swagger 2.0
move scanners specific for swagger 1.2 into folder
missing field: format in Items
let Getter out of ResourceListing
converter from 1.2 to 2.0
rename from Upgrade_1_2to2_0 to Upgrade
fix import path
remove renaming of '$ref'

it makes things more complicated.
remove renaming of '$ref'

it makes things more complicated.
scanner change

need to pass 'root of tree' when scanning.
make sure we won't traverse 'None' object
fix minor bugs and add draft version testing script
Merge branch 'swagger_2.0' of https://github.com/mission-liao/pyswagger into swagger_2.0
when calling update_field, we should raise exception when a field is not existed.
different objects for different 'items' in Schema and in Parameter

- refer to https://github.com/swagger-api/swagger-spec/issues/165 for
details.
- should be 'items', not 'item'
daily result, not finished yet.
in swagger 2.0, file should be lower case.
move objects.py back to v2_0 folder