Git-imerge

What's new in `git-imerge` 1.2.0 (since release 1.1.0):

* Add a `--commit` option to `git imerge reparent`, which lets a
sequence of merges be reparented.

* Add three more goal options: `border`, `border-with-history`, and
`border-with-history2`.

* Retain author information in more situations (i.e., whenever
retaining the commit message).

* Set up to release to PyPI.

* Switch tests to use `tox`.

* Make Python 3 more prominent than Python 2 in the docs.

* Add axes and labels to the text version of the `git-imerge diagram` output.

* Improve the test suite.

* Convert the README and TODO files to markdown.

Note that this release has actually (finally) been uploaded to PyPI :confetti_ball: Thanks to jdufresne for doing most of the work to set that up and my deepest apologies for not getting around to it until now.

This release includes:

* Don't be so picky about which branches can be merged together.

* Avoid storing the name of the default imerge in the Git configuration when it is unambiguous. This is mostly nice because Git leaves section headers behind when configuration sections are deleted, so using `git-imerge` used to make the config file untidy.

* Abstract out the interface to Git. This is only an internal refactoring, but will hopefully make it easier to add tests and/or implement some functionality using libgit2 rather than the Git command line.

* Various bug minor fixes.

Given the relative lack of automated testing, it's perhaps foolhardy to name this release 1.0.0. But I don't foresee having time to remedy the testing situation anytime soon, and I use `git-imerge` every day, so let's go.

- Add two new commands, `git imerge drop` and `git imerge revert`, for using incremental merging to get rid of unwanted commits from the branch history.
- When committing merges, default to `--no-edit`. The default can be changed via a new configuration option, `imerge.editMergeMessages`.
- If there is more than one merge base between the two branches, use the "best" one rather than refusing to start an imerge.
- `git imerge continue`: commit a merge even if its diff is empty.
- Improve docs.

Other changes and bug fixes:
- Avoid some redundant test merges.
- Fix some character encoding problems.
- Run `git checkout` with its `--quiet` option.
- Some fixes for bash completion.
- Install the bash completion script as part of `make install` and `make uninstall`.
- Handle `DESTDIR` in `make install` and `make uninstall`.
- Fix a Windows incompatibility when calling `git log` from `get_author_info()`.