tweet 6.x-3.1

Changes from 6.x-3.0:

• Use core theme function for displaying the icon; this should remove problems with the wrong URL being used
• #497876 Patch for showing ellipsis correctly (thanks ev)
• #543676 Invalid XHTML: onClick should be onclick by kaido24
• Added ability to use arbitrary text for "Post to Twitter"
• Changed all "else if" to "elseif" in PHP files per Coder 2.x
• #618628 Hashtags pulled from taxonomy
• Updated README

This release adds two settings to the module's settings page.