Adds support for bean regex tagging

[nmuesch]

Adds support for using the bean_regex syntax to capture groups for tags.

We currently support pulling in common attributes out of bean names, but this introduces the ability to specify any custom substring of a bean name to utilize as a tag on the associated attributes.

Ex:

init_config:
  conf:
    - include:
	bean_regex: 'Catalina:type=(.*?),*host=(.*?),context=(.*),*'
        attribute:
          spareNotFoundEntries:
            metric_type: gauge
            alias: tomcat.spareNotFound
          cacheMaxSize:
            metric_type: gauge
            alias: tomcat.cacheMax
        tags:
             TypeRegex: $1
             HostRegex: $2
             contextRegex: $3
             optional: tag

This will submit the metric tomcat.spareNotFound with tags hostRegex:<beanParameter> ,TypeRegex:<beanParameter>, and contextRegex<beanParameter> as well as the tag with key optional and value tag

[gmmeyer]

I have a single nit, but I think this looks like a pretty clean change.

[gmmeyer]

This is a stylistic issue, not a technical one. I don't love

""+i

I don't think it's very clear. I think it would be better to make it more clear:

Integer.toString(i)

[nmuesch]

Good call, that is definitely cleaner. Thanks!