Merge pull request #12 from goldingn/master

starting with raster functionality
Merge pull request #13 from goldingn/master

swapped the test raster for an Afripop 10km Kenya file
Merge pull request #15 from goldingn/master

added get.network function and doc, fixed kenya raster & added doc + minor edits
fixed bug in transcribing Simini eq 2 and corrected spelling of Simini
added function continuum.flux that calculates fluxes in more general suite of models from Simini et al 2013
Merge pull request #16 from TAlexPerkins/master

fixed bug in transcribing Simini eq 2 and corrected spelling of Simini
Merge pull request #17 from goldingn/master

tidying up and adding an example to the main helpfile
added help file for continuum.flux
Merge pull request #18 from TAlexPerkins/master

added help file for continuum.flux
added links in other docs for Alex' new flux functions, deleted the unnecessary html of the readme