git backup intro lesson now introduces the basic concepts of git structure
Update 01-backup.md
Change to working tree to match gitglossary
Add 05-undo.md as alternate way to explain git reset
Merge pull request #1 from jdcorless/master

Small changes to 01-backup.md and added 05-undo.md as an alternate
simplified discussion of git reset
spelling error
added table and some MD formatting to 01-backup.md, deleted 05-undo.md
Merge pull request #2 from jdcorless/master

added table and some MD formatting to 01-backup.md, deleted 05-undo.md
Update 01-backup.md
automergable version of intro git material
guide-shell/man: rudimentary man lesson

This commit includes work from David Worth.
ENH Add challenges
Expand description of SOURCE and DEST and one typo
MIN Fix Markdown code
ENH Add apropos challenge & wording fix
ENH Improvements & fixes
ENH Mention that 'n' searches for next match

As noted by @r-gaia-cs on github, the first hit for '-t' is not the
best one and the user must keep searching.
Merge branch 'master' of github.com:BillMills/bc
Merge branch 'master' of github.com:luispedro/bc into merging-man-lesson