Add mention of join() to the section of the manual about strings

This is one of the very useful functions which can be hard to find,
and very similar to repeat().
Merge pull request #9426 from JuliaLang/nalimilan/join

Add mention of join() to the section of the manual about strings
String docs: start to add crosslinks between manual and stdlib
Update README.md

`libgit2` does this and I think this fixes it without having to re-build everything.

Update README.md
Added warning message when ENV["TERM"]=="dumb". Resolves #9093
Merge pull request #9427 from goretkin/patch-3

Update README.md
Merge pull request #9361 from TravisBarryDick/warn_dumb_term

Added warning message when ENV["TERM"]=="dumb". Resolves #9093
Whitespace cleanup of README.md.
fix #8050
fix #9185. ah, numbers, it doesn't matter if they're correct, right?
Add a link to my slides from recent BAJU meetup
Fix LLVM3.6 build

(restores what was there before)
Merge pull request #9433 from JuliaLang/tk/deps-talk

Add a link to my slides from recent BAJU meetup
modified Types such that Year and Month are part of CalendarPeriod wrapped around Int
Week, Day, Hour, Minute, Second are wrapped around Real to allow for conversion between
Millisecond remained wrapped around Int
Ref Issue #9393