Tradingstrategy

- Remove old DataReplayer/DataResampler and cerebro resampledata_old and
replaydata_old which were using them
- Adapt docs and test to remove DataReplayer/DataResampler and document the
newer interfaces
- Add ``linesoverride`` parameter to enable redefining the lines of an object
at any stage. Allows removing OHLC default support
- Generalized GenericCSV to use the defined line aliases
- Generalized tick assignment to use the defined line aliases

- Closes 61 by checking datamaster against None to prevent operator
overloading to evaluate the object as False because line 0, contains a value
of 0 at index 0

- Closes 49 by setting the matplotlib backend to "tkagg" to avoid using other
non-tested backends
- io.StringIO instead of internally imported one from py3
- CSVDataBase unicode/bytes unification and also for YahooFinanceData feed
- yahoodownlaod tool bytes/unicode clarification and urlopen bug correction

- Fixes 55 and improves management of CSV subclasses opening a file from
other sources
- Sample which tests yahoo online downloading

- Fixes 51 - a trade may reopen a position but close a trade if overlapping
(different tradeid) trades are active
- Address Pull Request 52 by adding Py 2/3 MAXINT compatible "constant" which
is imported into TradeAnalyzer and used instead of sys.maxint
- Fixes 50 by correcting open/popen typo in StopLimit order

- Fixes 46 by adding a default of total.total = 0 to indicate that no trades
were executed and therefore no statistics
- Fixes 46 by adding a default of total.total = 0 to indicate that no trades
were executed and therefore no statistics
- CalendarDays filter implementation and added sample
- Removed gitter from README