miscellaneous typos
status command: improve help text
index.hdr.in: add code markup
index.hdr.in: (hopefully) non-controversial edits
index.hdr.in: slightly more controversial changes

 - Clarify wording in functions section
 - Use the term aliases rather than wrappers
 - Clarification of concepts and better? examples in variable expansion
 - Likewise in environment variables
 - Using the phrase builtin commands rather than builtins
 - Tidy up keybindings a bit
 - Another example in the history section
 - Remove TODO section in favour of mailing list, GitHub and IRC link
Tiny typo.
Fixed small typo

Fixed a small typo that I noticed in the design docs.
Pretty sure it was meant to say "turned off" instead
of "turned of".
Add a note about getting help through man pages
Merge branch 'zanchey-docs'

Conflicts:
	doc_src/index.hdr.in
Clarify "input/output methods" in documentation
Manually cleaned up Mercurial completions.
Add completions for cabal; closes #567
Added documentation for printf

Fix for https://github.com/fish-shell/fish-shell/issues/488
Avoid generating man page and help section for printf (to fallback on system man page for printf)
Formatting and style updates
Typos in the fish OS X package installer rtf file
Doc fix where wrong file was referenced in an example