Change acceptable values (#116)

Fix issue #116.

`block-indent`, `rule-indent` and `stick-brace` options now accept only these types of values:

 * `{Number}` of spaces;
 * `{String}` of whitespaces, tabs or new lines. If there is any other character in the string, the value will not be set.

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`colon-space` and `combinator-space` options now accept only `{Array}` of these types:

 * `{Number}` of spaces;
 * `{String}` of whitespaces, tabs or new lines. If there is any other character in the string, the value will not be set.

The first element of array sets spaces before, and second one sets spaces after.

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Tests and docs (both code comments and Readme) are updated.

![bunny-on-the-bed jpg](https://f.cloud.github.com/assets/872004/1654612/817c966c-5b50-11e3-801c-3f71139e0037.gif)