Fix clobbering of global 'tags'

Closes #78.
Improve multiline assignment handling

In the particular case of assignment, an if-construct (or similar)
should be indented differently that other kinds of continuations.
Handle an edge case with continuations
Fix bug with 'ignorecase' on

The pattern for the start of an "end" was being matched by a "Class"
constant.
Fix bizarre typos of "|" as "!"
Remove unneeded unmaps from b:undo_ftplugin

The "im" and "am" mappings are present a bit later in the file and the
"ic" and "ac" mappings are not relevant anymore.
Initial handling for closing brackets on the same line as code
Add documentation for ruby motions/text objects.
Enable im, am, iM, and aM in visual mode.
Indent functions with 2 spaces

To maintain consistency with the rest of the project.
Fix omnifunc's requirement test error messages.

Quick fix that could probably be better organised.
Restrict "do" blocks a bit

This solves the problem of a "do" being detected where it's part of a
method call or a symbol.

See: https://github.com/vim-ruby/vim-ruby/issues/92
Minor whitespace tweak
Handling for multiline splats
Fix some text erroneously marked up as option names in Omni docs.
Fix completion error

to reproduce:
x.f{$ # Invoke omni completion here
Merge pull request #100 from todesking/fix-global-arg-completion

Fix completion error about global variables
Fix escape_vim_singlequote_string

str argument is Symbol Object from Object.instance_methods etc,
and Symbol is undefined `#gsub`.
Highlight <%-# comments -%>

Closes #102.
Merge pull request #101 from joker1007/fix-escape-vim-singlequote

Fix escape_vim_singlequote_string