Resolve symlinks when determining CARTON_DIR

Makes sure that the correct directory is used when carton is symlinked
somewhere else.

Also use $0 instead of $BASH_SOURCE, as the latter is by documentation
only indented for bash functions.
Remove backticks
Use Emacs to determine the location of Carton
Merge branch 'fix-carton-dir'
Really list all packages

The second argument to package-menu--generate is either a list of
packages or `t`, meaning all packages.  `nil` is interpreted as empty
list of packages, thus the generated menu will be empty.  To list all
packages, `t` must be given.
Execute update in a temporary buffer

`package-menu--generate` populates `tabulated-list-entries` which is
buffer local.  Use a temporary buffer to fix and restrict the scope of
this variable.
Delete obsolete packages after upgrade
Merge branch 'fix-updates'
Update to version 0.1.0.