Fixes in alluvial_ts

Fixed argument documentation:
1. When documenting more than one argument with @param args need to be
separated with a comma.
2. Percent symbols need to be escaped with backslash.

Added rudimentary example.

Dropped require() call. Is "grid" really required?
Roxygenizations
alluvial_ts is now exported
Moved refugees to data and capitalized the name
Documented Refugees
Added reshape2 to Suggests, used in examples
Reformatted Refugees so can be loaded with data()
Fixed alluvial_ts examples

Examples are run if reshape2 is available.
Load Refugees with data().
Docs of alluvial_ts use outsourced examples from

examples/alluvial_ts.R
Merge branch 'master' of https://github.com/mbojan/alluvial
Refugee data description

Added source and data descriptions for Refugee dataset
Fixed minor bug when numeric category input given
Merge pull request #7 from geotheory/alluvial_ts_dev

Refugee metadata description
Updated Refugees docs and roxygenization
Added Robin as co-author
Fixed URL in Refugees doc
Removing misc rubbish