Inlined GetBodyMethodCallExpression,

since it was only used at a single call site.
Refactored GetMethodInfo

to GetMethodCallExpression, in order to make it useful from three other
call sites.
Also removed the XML documentation comments from the ExpressionExtensions,
since there's no reason to take on the overhead of maintaining XML
comments for non-public APIs.
Changed copyright year in .nuspec to 2014.
Corrected icon URL in .nuspec file.