initial implementation for doto macro
relates #567
test for doto macro
relates #567
documentation for doto
relates #567
Fixing `doto` to be API compatible with Clojure's `doto`
Shortening docstring
Adding myself as an author
Adding Version Added 0.10.1
Display python version & platform at repl startup

*hy/cmdline.py: At the repl startup the Python implementation & version
 is displayed along with the platform(os) information
Merge branch 'master' into pr/571

Conflicts:
	AUTHORS
	tests/native_tests/core.hy
Make ci builds faster by splitting requirements

Make travis builds faster by splitting requirements into
requirements-travis.txt, which contains all the requirements necessary
for running tests, documentation related packages are omitted and added
as a part of requirements-dev.txt

Additionally .travis.yml is modified to cache pip downloads, though this
feature is yet to be rolled out for the free tier
Merge branch 'master' into pr/585
Merge branch 'master' into pr/599