Add Haskell zipper exercise
leap-year? is a more clojure name than leap-year

The idiom seems to be to suffix predicate functions with a '?'
Merge pull request #967 from verdammelt/leap-year-name-fix

leap-year? is a more clojure name than leap-year
Test files can be snake case or camel case
Merge pull request #968 from meaganewaller/master

Test files can be snake case or camel case
Delete trailing whitespace
site_root uses HTTP_HOST header

Pretty sure this allows it to be whatever the client sees. For example,
this allowed it to work with pow.cx and also with the default Sinatra
localhost:4567, and sinatra run on a different port (rackup -p 1818).

It uses 'http://exercism.io' as a backup just in case this isn't
always set (might depend on the server, IDK).
add "log" to .gitignore
rewrite test suite for ruby hamming exercise
vary the test inputs, reorder tests to allow for smaller incremental changes
Merge pull request #977 from mjansen401/ruby_hamming_test_order

rewrite test suite for ruby hamming exercise
Merge pull request #976 from mjansen401/gitignore

add "log" to .gitignore
Merge pull request #980 from mjansen401/ruby_phone_number_tests

vary the test inputs, reorder tests to allow for smaller incremental changes
Merge pull request #974 from JoshCheek/smarter_site_root

site_root uses HTTP_HOST header
#859 set user.current if attempt is not complete
Update zipper exercise based on @etrepum's comments
Update code.rb

Updated to include objective-c file type '.m' so that submissions work.
Merge pull request #983 from mjansen401/set_current_in_seeds

#859 set user.current if attempt is not complete
Merge pull request #989 from redspike/patch-1

Update code.rb for Objective-c
Add missing instructions to contributing file