Trying to understand git diff syntax. Small update.

modified:   README.md
Set default behavior to compare <working tree> with <index>, and output shortened stats.

In this change we are able to use 'git size-diff' to output info about this
change.  The size summary below is comparing the working tree with the last
commit (HEAD).  This will be the default, and probably most used function of
this program. The rest of the functionality will remain however, so this tool
can be used to compare arbitrary size diffs between two commits, specified with
'git size-diff <tree-ish <tree-ish>'

This is also modeling the helpful type of code review request / commit message
I want to continue to see in the future.

-Title
-Long summary
-Block summary of edits
-Block suummary of size diff

The best way to track software is to make tracking every change painfully easy.
Everything we know about the potential change should make us more confident it's
in the best form it can be. Reviewers will need to see size improvements
numerically.

modified:   README.md
modified:   bin/git-size-diff.sh

git-size-diff:
 README.md            |    3 +++
 bin/git-size-diff.sh |   66 ++++++++++++++++++++++++++++++++++++++++++++++--------------------
 2 files changed, 49 insertions(+), 20 deletions(-)