git-info: POSIX compliance

Replace `echo -n` (non-POSIX) with an helper function `echon` echoing a
newline after given expression.
Update Readme.md

Original repo remote is named 'upstream' and not 'original' as Readme suggests.
Merge pull request #280 from valeriangalliat/feature/git-info-posix

git-info: POSIX compliance.
Merge pull request #281 from emilkje/patch-1

Original repo remote is named 'upstream'.
Use process-specific tmp file and clean up on exit

Fixes #279 using the suggestion from @hemanth, with some minor tweaks:

- I kept the leading . because I figured there was a reason it was put there originally.
- Changed the show_cursor method that's called when the process exits (prematurely or naturally) to be show_cursor_and_cleanup, and added a line to it that cleans up the tmp file.
Merge pull request #283 from e28eta/patch-1

Process-specific tmp file and clean up on exit.
More portable she-bangs.
added --no-color to git-delete-merged-branches
Merge pull request #287 from benjaminparnell/master

added --no-color to git-delete-merged-branches.
make release hook more flexible
Merge pull request #288 from dead-horse/release-hook

made release hook more flexible.
Use mktemp for temporary file creation.
Merge pull request #289 from mavant/feature/mktemp

Use mktemp for temporary files.
added changelog to release as optional flag

- rewrote the flags to contain multiple
- added -c as changelog option
Merge pull request #226 from tsldh/master

Added changelog -c flag to git-release.