Tradingstrategy

- Correct missing super in start some Data Feeds. Closes 27

- DivByZero function included to perform division without triggering
exceptions
- SessionFiller completed as data filter
- Corrections to WriterStringIO
- Final renaming of data filter API
- Reset of operators to stage1 to be able to run over same data again withoug
re-init
- Update data-replay/resample samples to use new filter API
- Rework of testcaes to use new filter API and run all combinations of
runonce/preload

- Comminfo passed down to trades for multitrade profit and loss calculation
for issue 226
- Addition of filters/processors (naming not final) to data sources
- (Re)Implementation of Resampling/Replaying as Processors - Old
Implementation still available
- Changed X axis formatting for Weeks/Months/Years
- DataFilter/DataFiller implemented as DataSources and also as
Filters/Processors
- DataFilter/DataFiller sample
- Time management improvement to address precision issues when isolating time
from coded datetime with new functions in LineBuffer

- Further refactoring of resampling (keeping previous parameter names
compatible) killing corner case for last bar still having the sub-bar
timestamp - Close 25
- Added sessionstart parameter to DataBase to complement sessionend
- Some module import refactoring to refer to main module
- Added DataFilter class
- Close 24 by enabling writer to handle Analyzer dictionaries which carry
non-string as keys
- Correct/enhance some of the samples

- Refactoring of minute/seconds/microseconds bar compression scheme to allow
time adjusted bars
- Added tick_last to datas - alias of tick_close
- resampledata and replaydata methods added to cerebro
- Added tick_last to datas - alias of tick_close
- Added multitrade support and sample
- Added helper time2num and num2time to complement date2num and num2date
- RelativeVolumeByBar Sample
- Corrected fromdate being set at the end of session
- Refactor some data feeds to use iterators and discard itertools.count
- Add dm/tm methods to LineBuffer to get numeric parts (int/fraction) of
numeric datetime representation
- Added sample datas with volume
- Corrected _orlogic for "Or" function and bool'ized And and Or
- Refactored starting points in running strategies
- Added queue/Queue to py3 compatibility
- Further rework of minute (and sub-minute) Data Resampling/Replaying
- Added tia/visualize-wealth/QSTK/TradingWithPython to README
- Added tick_last to set of tick variables (open/high/low/close)
- Added resampledata and replaydata to cerebro to avoid having to instantiate
DataReplayer/DataResampler

- Added TimeFrame for Ticks, MicroSeconds and Seconds
- Plot support for new Ticks, MicroSeconds and Seconds TimeFrames
- Removed flushing of sys.stdout on Win32 platforms to avoid interactions with
ipython (fixes 20)
- Reworked Resampling for TimeFrame Minutes (closes 19) and added Resampling
for Seconds, MicroSeconds and TickData
- Sample of plot-on-same-axis added
- Added pypy/pypy3 tests to Travis and added to to documentation
- Added sample which resamples tickdata