Shell#ask: support a noecho option for stdin
Update Ask documentation and change API to be :echo => false
Merge remote-tracking branch 'socialcast/stdin-noecho-support'

* socialcast/stdin-noecho-support:
  Update Ask documentation and change API to be :echo => false
  Shell#ask: support a noecho option for stdin

Conflicts:
	spec/shell/basic_spec.rb
Remove and_return from negative receive assertion.
Fix table spec.
Merge branch 'master' into gb-readline

Conflicts:
	lib/thor/shell/basic.rb
	spec/shell/basic_spec.rb
Test coverage for LineEditor::*.available?

Using Kernel.const_defined? instead of defined? makes this easier. Thanks
@cwninja
Move :echo => false support into LineEditors

:echo => false was added to the ask method in dbfdd30, this maintains that
behaviour with Readline support.

Tip o' the hat to @cwninja, we paired on this.