frankv gains by= argument, updated TODO in tests.
Added 'dense' and 'runlengths' rank types.
Hook frankv with 'dense' rank.
Merge branch 'Feature-760'

Conflicts:
	R/setkey.R
Added instructions to follow for Bug/FRs/PRs
Added "squashing commits" to PR.
Added links for PR/squash committing PRs
Updated link, and restructured for clarity.
Update Contributing.md
Updated README
Merge branch 'master' of https://github.com/Rdatatable/data.table
Updated README
Update Contributing.md
Remove 'order' argument from frankv
Booked shallow, na.omit in frankv. data.table tests to be added.
+ Major work to fread for embedded newlines and quotes inside quoted fields. Closes #810.
+ Field() now in one place.
+ Jump to middle and end now detects if landed inside quoted field with possibly very many embedded newlines.
fread's default skip=-1L changed to 0L
Removed library(reshape2,pos="package:base") from .onLoad.  Doesn't work after all and R CMD check thows NOTE. Will need to be user level until reshape2 pull request to make generic is on CRAN.
fread clearer 'file doesn't exist' message. Closes #486.
sep="." now works, closes #502