[DOC] Add general requirements doc.
Merge pull request #106 from ripple/requirements-doc

Requirements doc
[FEAURE] add setup-wizard http endpoint
[FEATURE] validate the existence of each config property

[TEST] check existence of each config property

[CHORE] move validation to API core
[TEST] postgres URL, ripple-rest URL and ripple address
[FEATURE] validate ripple address, porstgres url, ripple-rest url

[CHORE] breakup public http controllers.

[TEST] validate trust amount
[FEATURE] validate trust amount
[BUG] Default config params to {}.
[TEST] config property validation
[CHORE] add a success message
[BUG] validate config properties
[FEATURE] abstract verify sub-routines
[FEATURE] extend ripple address validator to the validator module
[FEATURE] implement wizard class that handles data validation and
verification

[CHORE] update minor version bump

[CHORE] clean up code
[CHORE] handle validation errors

[FEATURE] fire configure callback
[FEATURE] configure wizard sub-routines: generate/set/fund hot wallet,
set cold wallet
[FEATURE] _setColdWallet, _fundHotWallet, _setTrustLine

[CHORE] remove test cold wallet secret