[R-package] Updated package metadata in DESCRIPTION

[jameslamb]

I've been reading the DESCRIPTION section of Writing R Extensions, and found a few other fields we should be setting in our package metadata. I think this will help with #629 as well.

• changed tabs to spaces in author section of the DESCRIPTION
• fixed a minor typo in description of the package
• added NeedsCompilation: yes

The ‘NeedsCompilation’ field should be set to "yes" if the package contains code which to be compiled, otherwise "no" (when the package could be installed from source on any platform without additional tools). This is used by install.packages(type = "both") in R >= 2.15.2 on platforms where binary packages are the norm: it is normally set by R CMD build or the repository assuming compilation is required if and only if the package has a src directory.

• added Biarch: false

The ‘Biarch’ logical field is used on Windows to select the INSTALL option --force-biarch for this package.

--force-biarch attempt to build both architectures even if there is a non-empty configure.win

• added 'SystemRequirements: C++11'

Packages without a src/Makevars or src/Makefile file may specify that they require C++11 for code in the src directory by including ‘C++11’ in the ‘SystemRequirements’ field of the DESCRIPTION file, e.g. SystemRequirements: C++11. If a package does have a src/Makevars[.win] file then setting the make variable ‘CXX_STD’ is preferred, as it allows R CMD SHLIB to work correctly in the package’s src directory.

When we add content to Makevar[.win] (I'm working on that PR now actually), it will include CXX_STD. SystemRequirements is mostly a documentation field, similar to trove classifiers used in Python, so I still think it's worth having it.