Fix interaction with electric-pair-mode (issue #54)

Kudos to npostavs@github
make test: test both compiled and uncompiled variants
Create cask project; pull in ert.el to enable testing emacs23
ert-tests/test-electric-mode.el: add tests for electric indentation
.gitignore: ignore all *.elc
Suppress fontification messages in emacs23 test output
test-electric-mode: check interaction with electric-pair-skip-self flag