Merge pull request #2 from yarikoptic/master

very minor -- not even worth claiming an authorship ;-): spelling + trailing spaces
RF - remove old fix for github pages building
NF - add math_dollar extension
NF - add floating point explanation
Typo in range
Fix source command reference for powershell.
Updated gitwash build from gitwash repo
Fix for rst build errors from $VAR
NF - more explanation of inexect float integers
BF - typo for float64 integers
BF - a stray floating point was confusing
NF: floating point error

Not sure it makes sense, but hey.
RF - headings and some cleanup of fp error
More cleanup of float error
Edits to relative floating point page from Stefan
Quote dollars making mess of windows page
Improving path setting
Updates to windows 7 setup
NF - ctrl-tab mapped like mac
Improving path setting