Rename files to *.rst, so github renders better.

diff --git a/notes/cli.txt b/notes/cli.rst
similarity index 100%
rename from notes/cli.txt
rename to notes/cli.rst

diff --git a/notes/gsoc.txt b/notes/gsoc.rst
similarity index 100%
rename from notes/gsoc.txt
rename to notes/gsoc.rst

diff --git a/notes/spec.txt b/notes/spec.rst
similarity index 100%
rename from notes/spec.txt
rename to notes/spec.rst