Support for formatting and header spell-check

Added support for formatting - in other words, bold text will be
highlighted in bold, italic text in italic and so on.

Enhanced spell-checking so that headings can be spell-checked. It doesn't
make much sense to me to spell-check paragraphs, but not headings. Text
within B<> and I<> can now also be spell-checked too. Again, it seems
strange not to spell-check text simply because it is bold or italic.

These features are controlled by separate variables: perl_pod_formatting
and perl_pod_spellcheck_headings which would normally be set from your
vimrc file. The features are disabled by default to maintain compatibility.
POD formatting escapes syntax highlighting improvements.

- Closing > characters are now highlighted correctly.
- Formatting escapes like B<>, I<> can now be used in POD commands like
  =head, =item and so on.
Fix perlElseIfError when used in other syntax type

When used in the Mason syntax type, the way the perlElseIfError group
was handled caused any line beginning with 'if' to be highlighted as an
error.  This is due to the way Vim includes other syntax files.
perlElseIfError was marked as 'contained', but wasn't limited to a
specific group.  When perl.vim gets included, perlElseIfError is then
allowed to exist at what was formerly the top level.

Instead, make the errant '\s*if' of 'elseif' and 'else if' a part of the
perlConditional group, so that perlElseIfError can be confined to
containedin=perlConditional.

In Perl files, everything that should be marked as a perlElseIfError is
handled properly.  In Mason files, this prevents the erroneous
perlElseIfError highlighting for 'if', but only marks 'elseif' as an
error (the :syn-keyword perlElseIfError works; the :syn-match doesn't).
Merge pull request #105 from shlomif/master

Add =encoding to the POD syntax highlighting
Add tt2js syntax file
Fix the last changed date
Merge pull request #49 from njohnston/master

Support for POD formatting (e.g. highlight bold as bold) and spell-check enhancements
Merge pull request #80 from benizi/bugfix/elsif-when-included

Fix perlElseIfError when used in other syntax type
Set up compatibility mode
Skip failing anonymous folding tests for now
Add test for braces in heredocs

For GH #102, #43
Run highlighting tests with perl_fold on as well
Make sure subs don't match their ends inside of heredocs

Fixes GH #102
Fixes GH #43
Remove t from formatoptions and add ol

Closes GH #91
Make heredoc highlighting consistent with folding off/on
Update highlighter output for advanced.t
Update headers a bit
Direct users to the vim-perl group for requests
Rename README to README.md
Typo fix