import REPL.jl code

Fixes #1773 (Repl autocompletion for composite type fields).
Fixes #3652 (Segfault during TAB-completion on OSX).
Fixes #4477 (Tab completion for `using` should look up installed packages).
integrate REPL.jl code into Base
expunge readline
fix repl crash when tab-completing type field
fix repl crash when pasting trailing newlines
add old-repl path completion behavior to new-repl

Cf. #5343
fix buffer size bug in Readline.edit_replace

A symptom of this is if

    ext(c)<left><left><left><tab><enter>

is entered into a fresh session, the output is

    extrema (generic function with 2 methods)

instead of the expected

    ERROR: c not defined
repl: fix color detection on windows
repl: bind Delete key
repl: don't ignore --no-history option

Also, hoist all the using/imports to the top.
cleanup base/Terminals.jl

- fix cmove_* fallbacks
- remove unused Colors & Attributes code
- get rid of submodules
- deindent
add Google Compute Engine
Update README.md

Add section for building on Google Compute Engine, at least until OpenBLAS 0.2.9 is released and adopted with the patch for Sandybridge.
Add links to GCE and Julia Ferraioli's super blog.

Thanks @jakebolewski for the pointer to @juliaferraioli
clarify that Google does not own Sandybridge :)
clarify
Merge pull request #6301 from cmundi/gce

Help people get started with Julia on Google Compute Engine
Merge pull request #6270 from JuliaLang/mn/newrepl

new REPL
whitespace: deindent repl modules
rename Readline -> LineEdit

To prevent confusion with GNU Readline.