Update .gitignore for R history files
Add custom filled_contour function

This version works nicely with multipanel layouts. Doesn't set a colour
key yet.
Add an in-progress file to play with a fancy manipulate plot
Re-document() the functions and NAMESPACE
Switch to += notation for plus one in C++
Add burnin as argument instead of magic number
Add vulnerability threshold as argument instead of magic number
Move object declarations to top of script
Delete old commented code in paradox_pe_sim
Switch doubles to integers where possible
Update paradox_pe_sim to optionally output the time series too
Recreate RcppExports files
Add in progress testing code for new paradox_pe_sim function
Large restructuring of package; see details

I have remove paradox_pe_sim.cpp and get_pe.cpp since these are
now replaced by the one function that does both.

I have also renamed paradox_pe_sim to paradox_sim to be a little
less verbose.

I have added documentation and an example to paradox_sim and
re-run the documenation making for all files.
Merge pull request #5 from seananderson/master

Make many changes including package restructuring, returning time series, returning data frames, and code cleaning