HexValidation is too strict - #AARRGGBB is a valid color (with tranparency) in IE gradient calls

[pariser]

HexValidation requires colors to be either 3 or 6 hex digits. The following filter allows for supporting background transparency on IE:

filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=#99000000, endColorstr=#99000000);

See: http://msdn.microsoft.com/en-us/library/ms532879%28v=vs.85%29.aspx

I think this may solve the issue:

HEX_REGEX = /(#(\h{3}|\h{6}|\h{8}))(?!\h)/

[pariser]

@jdfoster4 Yep, I agree. I realize I can also just submit a pull request.

[sds]

Fixed by #215. Thanks for the report!