Merge pull request #5 from AlekSi/master

Small documentation tweak.
Parse Timestamps in DenseNodes.
Parse Timestamps in Ways and Relations.
Merge pull request #6 from AlekSi/time

Parse timestamps.
Removed performance section in README.md.
Update package documentation

Add keywords to first line for better search.
Merge pull request #7 from AlekSi/patch-1

Update package documentation.