document canonical name and move vars down to usage

Closes #20719.
Remove unused guard in canonical_name

Closes #20718.
use more env helpers
chruby 0.3.6

Closes #20729.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
ruby-install 0.2.0

Closes #20732.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
Copy env_proc when merging deps
Actually make the assertion we care about
s3fs 1.71

Closes #20740.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
youtube-dl 2013.06.27

Closes #20737.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
mr: use http url for git repository

Closes #20736.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
fftw: fix fortran

Closes #20727.
Show conflicting files on install if linking fails

Closes #18303.
Closes #20726.
Show tap/path for non-core formulae on build failure

Closes #16373.
Closes #20725.
Use 'path or URL' as tap for non-tap, non-core formulae
Misplaced manpages fail brewbot

Closes #20711.
Add :fortran requirement
Use :fortran

Closes #20731.
Closes #13621.
Update audit for Fortran dependency
Add Fortran ENV helpers
Use Fortran ENV helpers