Catch exception when connect to report server fails so that it can still work without it; fix the default ports for collector and query servers to make it work again.

[jianwu]

Which problem is this PR solving?

Resolves #47

Short description of the changes

The current version doesn't work out of the box. Mainly due to its dependency on the local reporter server. There's no documentation on how to set the local report server up. So it blocks most users to use this tool. This PR did the following changes to make it buildable and workable with default configurations:

1. Cache exception when connecting to local report server fails so make this dependency optional.
2. Fix the default port for the collector and query server. That value was correct, not sure why they are changed to a wrong value of 6831 which is supposed to be agent UDP port.
3. Set default SENDER to HTTP.