cleaning installer/shebang
Merge pull request #330 from mpapis/master

custom_shebang should not be used on binaries used in it - prevent loop
Merge pull request #384 from mpapis/clean_330

Clean up for #330
No reason darwin has a specific treatment.

Now, a version like unknown-freebsd or x86-openbsd will work.
Add some tests for the platform fix.
! Removed broken YAML gemspec support in `gem build`
Merge pull request #386 from Absolight/fixup-platforms

No reason darwin has a specific treatment.
Don't modify entries in $LOAD_PATH directly

It is not allowed in ruby 2.0.0 since r37481.

See also:
  https://bugs.ruby-lang.org/issues/7158
  https://bugs.ruby-lang.org/projects/ruby-trunk/repository/revisions/37481
Don't modify $LOAD_PATH. Sorry...

It is read-only variable.

This fixes "$LOAD_PATH is a read-only variable (NameError)" error
introduced by a1fa91f8b6a26d79c012a7126502be50fa606ab8.
silence
extract core_ext folder for better visibility
Merge pull request #395 from grosser/core_ext

extract core_ext folder for better visibility
Add "install -N" as short version of "--no-document"
Minor exception cleanup
Update Manifest
Merge pull request #394 from grosser/silence

silence
Support normal gem require without explicit 'gem "name"' for default gem

Let "test-unit" is a default gem.

Before:

    require "test/unit" # -> test/unit.rb of the standard library is loaded

    gem "test-unit"
    require "test/unit" # -> test/unit.rb test-unit gem is loaded

After:

    require "test/unit" # -> test/unit.rb of test-unit gem is loaded

Default gem related works are not completed. There are following
not implemented features:

  * Register the default gems
  * Support "gem contents" for RDoc
  * Block "gem uninstall default-gem"

This change shows what I want to do for implementing default gem. If
you accept this change, I will do the next works.

Note that I want to move Kerenel#require codes in
lib/rubygems/custom_require.rb to Gem::CustomRequire#run in the
future.
Fix a typo

unresoleved ->
unresolved

Pointed out by @drbrain. Thanks!!!
Don't create new class Gem::CustomRequire

Suggested by Evan Phoenix.

I'll re-propose this change later. I don't work on it with default gem
changes.
Add missing "lib/"