Added live autocompletion in editor. Bumped version to 0.2.1.

Modified README and RELEASE_NOTES to reflect the fact that shinyAce 0…

….2 is not yet available on CRAN.

Bumped up version number to 0.1.5.

Added 'Help' menu with 'About' submenu and 'Keyboard shorcuts' submen…

…u. Bumped release version to 0.1.4. Updated screenshot. Cleaned up keyboard shortcuts jQuery code.

Forced editor to refresh every 50ms to adjust text to available space…

… when switching between editor only and dual modes.

When editR cannot parse the markdown file without error, it shows the…

… last working version instead but displays it with reduced opacity to indicate an error.

Also added release notes, updated version number to 0.1.2, cleaned up some of the code.

Updated screenshot to show new 'View' menu.