rename to_formula to just formula
pass deps and options into the installer
move bottle-arch warning to install command
remove CannotInstallFormulaError

we'll need a similar sanity check, but that should happen prior to
instantiating the installer
remove conflict checking from installer

this should happen prior to instantiating the installer
install tests now use the actual installer
move warning out of installer
split out source and bottle installers
skip these tests for now