Quantiphy

- Fix nit in installer (setup.py).

- improve the ability of both ``quantiphy.Quantity.add()`` and ``quantiphy.Quantity.scale()`` to retain attributes.
- added *accept_binary* preference.
- support all preferences as class attributes.
- allow radix and comma to be replaced by adding *radix* and *comma* preferences.

- now support Quantity arguments with Quantity.extract().
- allow plus and minus signs to be replaced with Unicode equivalents.

- added RKM codes example.
- added *check_value* = 'strict' to quantiphy.Quantity.add().
- added backward compatibility for *form* argument of quantiphy.Quantity.render() if it is passed as unnamed argument.
- made quantiphy.Quantity.extract() a bit more general.
- reformulated exceptions.
- added support for binary scale factors and quantiphy.Quantity.binary().

- fixed bug in format that resulted in several format codes ignoring width
- follow Python convention of right-justifying numbers by default.
- add Quantity.add() (adds a number to a quantity returning a new quantity)
- added alternate form of string formatting.
- Change *show_si* to *form* (argument on Quantity.set_prefs() and Quantity.render()
- Added concept of equivalent units for unit conversion to documentation.
- Enhance UnitConversion so that it supports nonlinear conversions.

- enhanced Quantity.extract()
* non-conforming lines are now ignored
* values may be expressions
* values need not be quantities
* can specify a quantity name distinct from dictionary name
- enhanced the formatting capabilities.
* added center alignment
* added *p* format
* added *show_commas* preference.
* added *strip_zeros*, *strip_radix* to Quantity.render()
* added Quantity.fixed() method
* added Quantity.format() method
* support any format specifier supported by Python for floats