Bump version to 0.3.1
ADC16.chip_num now accepts numeric strings

In addition to all the various "chip spec" formats already supported,
ADC16.chip_num now also accepts numeric strings '0' through '7'.
Use Strings instead of Symbols for default Range

Ruby 1.8 does not allow Symbols to be used in Ranges, so change the
default chip Range from :a..:h to 'a'..'h'.
Fix splat operator usage for Ruby 1.8

Ruby 1.8 does not allow any arguments to follow the splatted arguments
from an Array, so any trailing arguments (such as an options Hash) must
be puhed onto the end of the Array instead of passed as a trailing
arguments.
Remove unused code from adc16_status.rb
Create ADC16#sync_chips method

Refactor the sync part of ADC16#calibrate into its own method named
ADC16#sync_chips.
Make adc16_plot_taps.rb sync the chips

adc16_plot_taps.rb used to walk the delay taps only.  This left the
IODELAY blocks setup to deskew the data properly, but they were not
necessarily bitslipped to ensure proper framing the the 8-bit samples.
Now that ADC16#sync_chips is its own method, adc16_plot_taps.rb can use
it to bitslip the channels to ensure that the samples are being captured
correctly.
Bump version to 0.3.2
Bump version to 0.3.3