Remove repeated code for API requests

Many lines of code were removed or reduced down to instead use these two functions:
 * send_post_request(url, data)
 * send_get_request(url)

The benefits of this refactoring should be obvious.
Fix str/bytes issues

Remove errors related to bytes and strings.

Also did a minor touch-up of the printed output.
Add `import_some_issues`

Calling the class with parameters will add the specified issues based on their id.

Calling with no parameters will import ALL open issues.
More prettifying

Mostly visual changes
Move options to separate `config.py` file

That way, modifying or updating `gh-issues-import.py` won't affect
the password, and won't publish the password for all to see in public repos.

Code taken from https://github.com/dliuzzi/tools/commit/5bbfe04775d83343268af35dd6b0a552a0ee43b4
created as a new commit, rather than a cherry pick or merge to avoid merge conflicts.
Issues are now exported chronologically

Original commit by 'dliuzzi' (http://github.com/dliuzzi)
in https://github.com/dliuzzi/tools/commit/5d190cdc994240379d96df2206fcc218cabb09a9
Merge 'dev' into 'master'

It's stable, I have been using the version in 'dev' for a while now.
Move `gh-issues-import` to its own repository

The code has been moved to [IQAndreas/gh-
issues-import](https://github.com/IQAndreas/github-issues-import/)