Add command-line flags

[tmck-code]

Context

Edging closer towards a useable cli tool, and not just a barebones POC

This adds some handy-dandy arguments to pokesay-go, initially these are just related to the text wrapping & formatting.
In particular, use -nowrap for a nice speed increase.

Changes

Usage of ./pokesay:
  -fastest
        run with the fastest possible configuration (-nowrap -notabspaces)
  -notabspaces
        do not replace tab characters (fastest)
  -nowrap
        disable text wrapping (fastest)
  -tabwidth int
        replace any tab characters with N spaces (default 4)
  -width int
        the max speech bubble width (default 80)

• Added a -fastest flag which will switch all the flags to whatever the fastest mode is (if applicable)
  • currently it's equivalent to -nowrap -notabstop
  • -nowrap makes a nice difference
  • -notabstop is statistically insignificant, unless the size of the text is huge

Benchmarks

# test data:
# for i in {1..1000}; do fortune >> f.txt ; done

Summary
  'cat f.txt | ./pokesay -fastest' ran
    2.08 ± 0.27 times faster than 'cat f.txt | ./pokesay'
    2.37 ± 0.32 times faster than 'cat f.txt | $HOME/bin/pokesay'