Merge pull request #33 from jread-usgs/master

updated install instructions for x64 ncdf4
Merge pull request #34 from jread-usgs/master

v0.2.2, added 'tools' package and field val methods
Merge pull request #35 from jread-usgs/master

v0.2.3 support for plotting heatmaps
Don't need dev.off() in the function. 

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