Add new regular expression syntax groups

This adds new syntax ids for matching boundaries, back references,
zero-width modifiers, quantifiers, and grouping.

Also, jsSpecial has been patched to support null and control characters.
Contain jsRegexpOr
Adds fixes for multi var indent for comma first

Also comments out the multi var indent
Adds concealing to some JS statements
Makes the conceal syntax optional

To use syntax concealing one must now put this line in their `.vimrc`

    let g:javascript_conceal = 1

Fixes #72
Merge pull request #70 from noprompt/noprompt-regexp

Add new regular expression syntax groups
detect javascript from shbang
Fixing multiline differentiation, fixes #77

This patch is not directly mine, it is from @drslump on issue #77 - see https://github.com/pangloss/vim-javascript/issues/77#issuecomment-18255638 for details

In testing, this change works beautifully to fix #77
Merge pull request #78 from brianarn/indent-fix-77

Fixing multiline differentiation, fixes #77
merge from upstream