Support http url characters as trace entity names per RFC#1738

I'm getting the following, running aws-xray-sdk==1.0:

`Removing Segment/Subsugment Name invalid characters from https://my.elasticsearch.cluster/iis_log_prod-*/_search`. Elasticsearch does use a bit weird url naming, but it AFAIK they're fully conformant.

For info, i'm not manually naming xray-subsegments, but I'm assuming this happens under the cover when I use the `requests` package to invoke url requests.