Release 2.2

Release 2.1

Merge pull request #101 from mnewt/eshell-path-env-in-buffers

Set each instance of the buffer local variable eshell-path-env

Don't use -i by default with Fish (see #87)

Correct a function name in the README

Preserve "" env var values: don't map them to nil

See #31

Don't break if $SHELL is unset at load-time

Fixes #20

Add note about fish and tcsh to README

Append exec-directory to exec-path, as is conventional

Use -d in place of --login for tcsh (fixes #7)