Fix deprecation error.

Without fix, this error message appears:

    bin/vim-ruby-install.rb:15:in `<main>': Use RbConfig instead of obsolete and deprecated Config.

    uninitialized constant Env::CONFIG
    Try 'ruby bin/vim-ruby-install.rb --help' for detailed usage.
Reformat installer.

Replace tabs with spaces. Ensure comments are properly lined up with code.
Merge pull request #153 from Ichimonji10/master

fix and reformat installer
Fix keyword symbols after parentheses

In response to the comment in #144.
Remove s:save_cpo when we're done with it
Simplify ruby*Constant syntax group matching
Add a g:ruby_no_hanging_indent option

Setting this to 1 will change the indentation behavior so that
pressing Return and adding a ) after the following code

    invoice = FactoryGirl.create(:invoice,

no longer aligns the ) with the (, but places it at the same level as the above
line. A similar thing will happen for

    some_long_variable = case

instead of indenting two spaces after the beginning of the `case`.