Add forceSynch option which will autosave to textarea.

Since this is built on CodeMirror I opted to use CodeMirror's save
behaviour rather than pulling the value and stomping on the textarea's
innerHtml.

Fixes sparksuite#193

Author: cbadke

README.md

@@ -78,6 +78,7 @@ simplemde.value("This text will appear in the editor");
   - **code** Can be set to  ```` ``` ```` or `~~~`.  Defaults to ```` ``` ````.
   - **italic** Can be set to `*` or `_`. Defaults to `*`.
 - **element**: The DOM element for the textarea to use. Defaults to the first textarea on the page.
+- **forceSynch**: If set to `true`, force changes made in editor to be saved back to original textarea.
 - **hideIcons**: An array of icon names to hide. Can be used to hide specific icons shown by default without completely customizing the toolbar.
 - **indentWithTabs**: If set to `false`, indent using spaces instead of tabs. Defaults to `true`.
 - **initialValue**: If set, will customize the initial value of the editor.