Add Transit JSON/MessagePack support

This PR adds Transit JSON/MessagePack support. `:form-params` encoding
is triggered by setting the `:content-type` to either `:transit+json` or
`:transit+msgpack`. Response body decoding is triggered by setting `:as`
to `:transit+json`, `:transit+msgpack` or just `:auto`.

The `wrap-form-params` middleware has been refactored to call the
`coerce-form-params` multi method to enable pluggable form encoding in a
similar fashion as we have done with `coerce-response-body`.
Merge branch 'pr/215'
Miscellaneous bikeshedding, update changelog
drop support for clojure 1.4.0, start testing 1.7.0-alpha1
*really* drop 1.4 support by removing it from project.clj
Release 1.0.0
Bump to 1.0.1-SNAPSHOT
Add `:decode-cookies` option to skip cookie header decoding
REPL require code has extra single quote
Merge pull request #217 from blissdev/master

REPL require code has extra single quote
Add support for proxy-user and proxy-pass to authenticate to proxies

See: #153
added download with progress example
renamed conj* to insert*
no more dependencies comment
added output example into progress download example
added output example of bar with unknow content-length
Merge branch 'pr/220'
Exclude clojure.core/update from client ns

Clojure 1.7.0-alpha2 added the update method, this removes the warning
when using clj-http with it.

Fixes #222
Fix :json-strict-string-keys

Make decoded JSON keys actually be strings in :json-strict-string-keys
mode.  Prior to this patch you'd get strict parsing behaviour, but the
keys would still be keywords (looks like copy-paste bug from two lines
above).

Also added very basic tests to cover string-keys.
Add an example of a PUT request to the readme

Fixes #228