some parsing and formatting functions that could be useful for ISO-8601 formats.

These functions are not sacred - maybe they are  suggestions about how it might be implemented deeper in the code.
small correction to examples
Merge pull request #148 from imanuelcostigan/master

origin is now UTC not GMT
Update DESCRIPTION

Update version number
Wrote date_decimal, which reverses decimal_date. Fixes #149.
pointless commit
fixing merge conflicts
Edited as.interval to handle NA input. Changed as.period.difftime to rely on seconds_to_period. Created methods for as.period and as.duration to handle logical input. Created as.character methods for periods, durations and intervals.
Wrote summary.Duration with tests.
Wrote summary.Interval with tests.
Edited c.Period to coerce non-period objects to periods (when possible). Wrote seconds_to_periods. Wrote summary.Period with tests.
Fixing typos
Merge pull request #143 from ijlyttle/master

support for ISO-8601-formatted instants
Generated new documentation related to ymd_hms_z pull request features and recent changes.
Exported c.POSIXct and added some missing docs.