Add new scripts for git operations
Relocate git-diffall

Relocated git-diffall and updated it to latest from

https://github.com/thenigan/git-diffall
Add more useful git scripts
Relocate git helpful scripts
Add and update ack, gem, screen rc files
Add nojoinspaces

Insert only one space when joining lines that contain
sentence-terminating punctuation like `.`.
Add helpful vim scripts