Version 3.6.4

  Merge pull request #84: Asynchronous tags file updates! \o/   http://github.com/xolox/vim-easytags/commit/1a09c98  Support for keyword based syntax highlighting (much faster):   http://github.com/xolox/vim-easytags/commit/b6f8757  Deduplicate syntax keyword arguments:   http://github.com/xolox/vim-easytags/commit/0a64a81  Filter out forbidden syntax keyword arguments:   http://github.com/xolox/vim-easytags/commit/2ff14b3  Bug fix: Restore default syntax pattern prefix/suffix (word boundaries):   http://github.com/xolox/vim-easytags/commit/a18d9f7  Use timers to identify slow[est] parts of vim-easytags:   http://github.com/xolox/vim-easytags/commit/83e8cf3