Implemented ts_api:get_user/2, ts_api:put_user/1, and ts_api:post_user/1.

Created a utility function for OK results, ts_api:make_json_200/2
Created ts_common:new/1 and ts_common:update/1 to generalize record creation and update.
Refactored ts_timeline:new/1 and ts_timeline:update/1 to use the ts_common functions.
Implemented ts_json:record_to_ejson/1 and ts_json:ejson_to_record/1 for ts_user records.
Implemented ts_user module.

src/ts_user.erl

@@ -1,5 +1,5 @@
 -module(ts_user).
--export([]).
+-export([create_table/1, new/1, update/1, lookup/1, list/2]).
 
 -include("ts_db_records.hrl").
 -include_lib("stdlib/include/qlc.hrl").
@@ -9,4 +9,38 @@ create_table(TableOpts) ->
         TableOpts ++ [{attributes, record_info(fields, ts_user)},
                       {type, ordered_set}]).
 
-%new(TR = #ts_user
+new(UR = #ts_user{}) -> 
+    case mnesia:dirty_read(ts_user, UR#ts_user.username) of
+        [ExistingRecord] -> {error, {record_exists, ExistingRecord}};
+        [] -> mnesia:dirty_write(hash_input_record(UR))
+    end.
+
+update(UR = #ts_user{}) -> 
+    case mnesia:dirty_read(ts_user, UR#ts_user.username) of
+        [] -> no_record;
+        [_Record] -> mnesia:dirty_write(hash_input_record(UR))
+    end.
+
+lookup(Username) ->
+    case mnesia:dirty_read(ts_user, Username) of
+        [] -> no_record;
+        [User] -> User
+    end.    
+
+list(Start, Length) -> ts_common:list(ts_user, Start, Length).
+
+hash_input_record(User=#ts_user{}) ->
+    % generate the password salt
+    Salt = generate_salt(),
+    % hash the password
+    HashedPwd = hash_pwd(User#ts_user.username, Salt),
+    % create a new User record
+    User#ts_user{pwd = HashedPwd, pwd_salt = Salt}.
+    
+generate_salt() ->
+    "This is a worthless salt value only suitable for testing.".
+
+hash_pwd(Password, Salt) -> do_hash(Password ++ Salt, []).
+
+do_hash([], Hashed) -> Hashed;
+do_hash([Char|Pwd], Hashed) -> do_hash(Pwd, [Char + 13 | Hashed]).