New types Account, Currency, Directory:
* New tagged uint types.
* Extract to_string functions from header to hide dependencies.
* Include what you use and C++11 for cleanups.
Update state during pathfinding
During playback close ledger before accepting
Restore checkpointed ledger under all paths in PathFind.
Tighten up some serialization checks
Improvements to HTTP parsing
Structured Overlay support:
* Add Peer Protocol detector
* Add RIPPLE_SINGLE_IO_SERVICE_THREAD setting
* Preliminary HTTP header parsing logic (disabled)
Update ripple-lib integration tests
New integration tests:
* New tests for autobridging and freeze
* Discrepancy detection tests
* Don't let Mocha suppress load time errors
In JSON, output unprintable currency codes as hex
Fix a case where we put an extra node in the SHAMapDiff
Add new memo restrictions
Add README.md for ledger process
Update Sconstruct
Cleanup confusion of ledger base versus ledger header

The "ledger header" is the chunk of data that hashes to the
ledger's hash. It contains the sequence number, parent hash,
hash of the previous ledger, hash of the root node of the
state tree, and so on.

The term "ledger base" refers to a particular type of query
and response used in the ledger fetch process that includes
the ledger header but may also contain other information
such as the root node of the state tree.
Remove boost::hash_value() overloads.
This addresses https://ripplelabs.atlassian.net/browse/RIPD-102
Fix base log partition severity
Add preliminary Structured Overlay docs
HTTP support improvements:
* Case insensitive equality, inequality operators for strings
* Improvements to message_parser
* Tidy up HTTP method enumeration
* boost::asio buffer helpers
Structured Overlay work:
* New I/O paths for client and server role
* New handshake_analyzer detects the peer protocol
* New basic_message class for parsing and storing HTTP messages
* Conditional compilation for selective feature enabling.