#61 0.9.18 does not support @keyframes tag and looses formatting

[shivaraj]

Please add support to @keyFrames. Using 0.9.18 jar, any @keyframes tags while parsing are being recognised as "CSSUnknownRuleImpl".

@keyframes background900
{
** 0% { background-position:0 0; }
100%** { background-position:0 -900px; }
}

In the above example, if i iterate this rule it removes the "%" sign and it breaks the entire animation. 
The output looks like this
@keyframes background900
{
    0  { background-position:0 0; }
    100 { background-position:0 -900px; }
}