Update CESens.R

Commented out library calls
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Updated revision number
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Update to reflect recent changes
Update CESens.R

Commented out "require(tcltk)" in file.nav() function to eliminate error message at CRAN.
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Adjusted "SystemRequirements" section to more clearly describe supported operating systems.
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Update DESCRIPTION

Updated revision date
Merge pull request #2 from lisahenn/master

Update to 1.0.2 to address CRAN request.