Remove Regex "matched text"

[mclotworthy]

In the case that all capture groups from a regex are optional and not supplied in the checked text; context.params[0] will be the "matched text" of the regex. Deleting property 0 from params before populating params prevents this.

https://github.com/visionmedia/page.js/issues/538

[coveralls]

Coverage increased (+0.4%) to 92.531% when pulling f2ce7424c7a76ce4c03afa00793ad6cdd15bea2b on mclotworthy:master into aee9de80a891f42b78c8605f139438e726d21f60 on visionmedia:master.

[matthewp]

Thanks! Think you could add a test?

[matthewp]

Perfect, thank you!