fix File.readable? when native is disabled

this readable? method now follows the same pattern as writable?, file?,
directory? and exists? and uses the respective FileResource directly.

fixes #2040 and #1983

Sponsored by Lookout Inc.
get better pattern matching for uri-like path for jirb

if the path to jruby-complete.jar contains a space the various
uri-like path strings do not match (file: or no protocol, ' ' or '%20')
should be treated equaly.

Sponsored by Lookout Inc.
If presumed URI does not decode, it's not a URI. Fixes #2264.
Add a spec:ruby:fast target that avoids subprocess-spawning specs.

Conflicts:
	rakelib/rubyspec.rake
Update list of slow language specs.
Add fast rubyspec for 1.8 mode and make travis use them.
Peel off options hash passed to Open3.popen3.

Fixes #1290.
Fixes #1547.
Merge remote-tracking branch 'origin/jruby-1_7'

Conflicts:
	.travis.yml
	antlib/spec.xml
	rakelib/rubyspec.rake
	spec/jruby.1.8.mspec
Update to RubyGems 2.4.4.
Apply fix from rubygems/rubygems@d96c57c temporarily on master.