i18n: Add locale object

It provides the following features:

  * Loads translation messages from .po file.
  * Translates a message into the locale.
i18n: Add i18n supported text

It provides the following features:

  * Extracts translation messages from wrapped raw text.
  * Translates wrapped raw text in specified locale.
i18n: Add pot formatter

The following options are added:

  * --locale
  * --locale-data-dir

You can generate .pot (PO Template) file by the following command:

    % rdoc --format pot

You can find .pot at doc/rdoc.pot.

You can create .po from .pot by msginit provided by GNU gettext. Here
is an example command line to generate .po for Japanese:

    % mkdir -p locale/ja
    % msginit --input doc/rdoc.pot --output-file locale/ja/rdoc.po --locale ja

You can also use rmsginit provided by gettext gem instead of msginit:

    % mkdir -p locale/ja
    % rmsginit --input doc/rdoc.pot --output locale/ja/rdoc.po --locale ja

rmsginit is implemented by pure Ruby. So it is more portable for
Rubyists.

.po should put locale/ja/rdoc.po or locale/ja.po. If there are both
files, the former is used.
i18n: Support translation by .po

You can translate RDoc documentation by locale/#{LOCALE}/rdoc.po. For
example, locale/ja/rdoc.po is for ja locale.

If you have locale/ja/rdoc.po, you can generate documentation in
Japanese by the following command:

    % rdoc --locale ja
i18n: Remove needless with_line

It breaks Ruby 1.8 support.
i18n: Sort PO entries to use stable expected value

Ruby 1.8's Hash doesn't have order.
i18n: Extract MessageExtractor to another file
i18n: Extract PO to another file
i18n: Extract POEntry to another file
remove execute bit from darkfish images

Some PNGs has the execute bit set. Reset the execute bits for
uniformity.
Fix outdated comment
Remove role="banner" from navigation sidebar

From the Techvision review:

Issue:

There is no banner on the page.

Solution:

Remove banner role
Remove <h3> from Pages, Classes, Methods nav links

From the Techvision accessibility review:

> Issue:
>
> There are headings for Home, Pages, Classes and Methods link in
> navigation. Home has heading level 3 and other three have heading
> level 4. So, Pages, Classes and Methods being different links, screen
> reader announce those as one link like "Link Pages Classes Methods".
> It should announce "Link Pages" "Link Classes" etc.
>
> Solution:
>
> Remove headings of all 3 links. As these are navigation links, there
> is no need of headings here.
> You may address these links as quick navigation. And the div will look
> like: <div id="home-section" role="region" title="Quick
> navigation"></div>

Note that I gave the existing home-section in a role="region" and
created a new <div> to replace the existing <h3>.  This will need
further review by Techvision.
Switch to Gem::TestCase#util_spec from quick_spec

quick_spec will eventually go away, so we want to take care of this now.
Fix tests following @736b5f6

util_spec requires a version argument on RubyGems 2.1.x and older, so
when I ran the tests in ruby-trunk they did not fail here.  Now I've
stuck the version back in.

I shouldn't commit tired, but it's easier than dealing with other
issues.
Document `rake` and `rake clean` commands to generate and delete RDoc
parsers using Rake.

This should fix #255 and similar issues.
Add failing test for #259
Merge pull request #258 from ktdreyer/darkfish-permissions

remove execute bit from darkfish images
Do not strip regexp literal options [fixes #259]

Ensure that the lexer includes any option, like /foo/i,
when lexing regexp literals.
Correctly handle multiple options

"if is a degenerate while" :D