Add some support for linux

Most of the effort has gone into differences with paths.

What works:

        export R_HOME=/lib/R
        fsharpi

TODO:
        Use `which` to find R when R_HOME not set
        There appear to be some problems when using fsharpc
Update RInit.fs

Accidentally left in some debug code
Merge pull request #56 from sergey-tihon/master

Fixed issue #55 - Build script was updated
Update release notes
Merge pull request #57 from jpalmer/master

Code to make the type provider work in Linux
Refactor unix/mac detection to be more readable
Increment version, add one more directory to load script
Fixed typo

Thanks for mentioning me and FAKE.
Merge pull request #61 from forki/patch-1

Fixed typo
Added new subsection "Creating and passing an R function"
Merge pull request #62 from renkun-ken/patch-1

Adding new subsection "Creating and passing an R function"
Make snippet colorized