Tradingstrategy

- Add rounding control to YahooFinanceCSVData and update docs. Closes 138
- Sharpe Ratio external testing sample. Addresses 137
- order_target_api, sample and cos. Closes 134

- Added Any, All, Reduce, function replacements
- Added AnyN, AllN, ReduceN indicators
- Aliased Highest -> MaxN, Lowest -> MinN
- Added VChartfile Store and Feed improving over existing feed
implementing the store pattern and fetching the basepath location
from the registry if possible
- Some docs improvements/corrections
- Add a generic Store to let stores subclass
- Add a Chainer, RollOver data feed and sample
- Add shortcuts for some subpackages: indicators -> ind, observers -> obs
strategies -> strats, commissions -> comms
- Add framework for analyzer testing and tests for 2 analyzers: SQN,
TimeReturn

- Finalize Oanda integration
- Allow simulated orders (meant to fetch initial positions from live brokers)

- Add support for credit interest rate (125), with update of docs, sample,
support in broker and btrun
- urlencode tickers for yahoo downloads (feed and tool)

- Added indicators (3): Hull MA, ZeroLag Indicator, Dickson MA
- Added control of object cache to cerebro (default deactivated)
- Refactored the support for "next" only indicators
- Typos and Docs updates (also from pull-requests)

- Refactor bt.signals to bt.signal (keeping compatibility for prev uses)
- Improve writer to write non-string lists and fetch headers after anylzers
- Add base bt.Signal strategy class for easier subclassing
- Update btrun to support signals/slippage/flushing, update feeds and minors
- Correct writer collections of analyzers parameters
- Correct reverse overloaded operations in stage2
- Some docs/docstrings corrections