Expansion of intro, with sections for roadmap and source code strategy.
Merge branch 'master' of https://github.com/kwan0xfff/fmtk into math
Point from README to intro.
Improvements to quickstart/provisions via fmtk-qs.

* In provisioning, detect more symlink errors.
* Fix incorrect symlink dependencies.
* Workaround for default build directory.
* pylint
Add build provisioning workarounds.
Merge branch 'master' of https://github.com/kwan0xfff/fmtk
Merge branch 'math'
Add libfmtkMath to generated symlinks.
Clarify parts of build workarounds.
Link-related typo.
No HTML in source; all generated from rST.
Put message about "tksrc" in top-level Makefile.
Example command: standard atmosphere table.
ignore tksrc
Add "cmds" to subdirs; add "tskrc" symlink reminder.
Exit make loop on subdir make failure.
Use inline ctor/dtor for Cart3f classes; resolves link-time conflicts.
Add "SimpleMotion" simple motion propagator.
Statically define BUILDROOT before build.
Comment out "const int ZERO". Not currently used.

Leaving it in causes compile fails on some platforms.