- dropped build scripts and files for single-file distribution.
- updated git pre-commit hook to run "make check" instead of "make dist"
- renamed zero-input-framework to zero-input. This is to conform "there
  should be a library with the same name as package name" rule.
- rename .el.in to .el.tpl.
  melpa build process will do something on .el.in, which I do not expect.
- "make tar" is a little messy because emacs doesn't support git archive
  generated tar file.
- add zero-input-pkg.el in git, melpa build hangs when this file is not
  present.

since this is a backward incompatible change, I set version to v2.0.0.
all symbols and functions is now prefixed with zero-input.

This change is suggested by melpa reviewer.