Parse Site information from IGC file

Hi,

currently the igc-parser is not parsing the information about the flying site from the igc file.
E.g.:
```
HOSITSite:Bassano
```
According to the Specification it describes: 
```
SIT H Site, Name, region, nation etc
```
http://www.ukiws.demon.co.uk/GFAC/documents/tech_spec_gnss.pdf

Are there plans to implement parsing of this?

Thanks for the great module! :)