Mention antigen-hs in readme

Since antigen was what made my zsh-loading time unbearable, I thought it would be nice to share this little plugin manager I wrote on my own. I would also like to invite other programmers to share their own plugin manager implementations here (as afaict, antigen is the only well-known software for this).
Merge pull request #84 from Tarrasch/patch-2

Mention antigen-hs in readme
fixed curl url for installation
added -L to install curl command
Merge pull request #86 from schmitzjake/master

fixed curl url for installation
Merge commit '8f19e93f6e608f60b71cf0a01cab7f8122638b7c'
Make no-local-clone sourcing consistent with clone sourcing
Merge pull request #91 from willghatch/fix_location

Make no-local-clone sourcing consistent with clone sourcing
If the given location is a file rather than directory, source it.
update readme to show that loc can be a file
remove btype arg from -antigen-load, since it's now unnecessary

The tests in bundle-syntaxes.t checked that -antigen-load was receiving
btype=plugin for every test, so it provided no useful coverage anyway
(for that aspect).  The parser tests for btype, so that functionality is
covered elsewhere.
Merge pull request #92 from willghatch/source_file

If the given location is a file rather than directory, source it.
Use emacsclient everywhere for good
Merge commit '30098c1d9955b8548aa827588c0d2c9be077c6f2'