adding gigasecond, not sure if it works

Signed-off-by: vsoch <vsochat@stanford.edu>

elm/gigasecond/README.md

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+# Gigasecond
+
+Given a moment, determine the moment that would be after a gigasecond
+has passed.
+
+A gigasecond is 10^9 (1,000,000,000) seconds.
+
+## Elm Installation
+
+Refer to the [Installing Elm](https://exercism.io/tracks/elm/installation) page
+for information about installing elm.
+
+## Writing the Code
+
+The code you have to write is located inside the `src/` directory of the exercise.
+Elm automatically installs packages dependencies the first time you run the tests
+so we can start by running the tests from the exercise directory with:
+
+```bash
+$ elm-test
+```
+
+To automatically run tests again when you save changes:
+
+```bash
+$ elm-test --watch
+```
+
+As you work your way through the tests suite in the file `tests/Tests.elm`,
+be sure to remove the `skip <|`
+calls from each test until you get them all passing!
+
+## Source
+
+Chapter 9 in Chris Pine's online Learn to Program tutorial. [http://pine.fm/LearnToProgram/?Chapter=09](http://pine.fm/LearnToProgram/?Chapter=09)
+
+## Submitting Incomplete Solutions
+
+It is possible to submit an incomplete solution so you can see how others have
+completed the exercise.

elm/gigasecond/elm.json

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+{
+    "type": "application",
+    "source-directories": [
+        "src"
+    ],
+    "elm-version": "0.19.1",
+    "dependencies": {
+        "direct": {
+            "elm/browser": "1.0.0",
+            "elm/core": "1.0.0",
+            "elm/html": "1.0.0",
+            "elm/parser": "1.1.0",
+            "elm/regex": "1.0.0",
+            "elm/time": "1.0.0",
+            "justinmimbs/date": "3.2.1",
+            "rtfeldman/elm-iso8601-date-strings": "1.1.2"
+        },
+        "indirect": {
+            "elm/json": "1.0.0",
+            "elm/url": "1.0.0",
+            "elm/virtual-dom": "1.0.0"
+        }
+    },
+    "test-dependencies": {
+        "direct": {
+            "elm-explorations/test": "1.0.0"
+        },
+        "indirect": {
+            "elm/random": "1.0.0"
+        }
+    }
+}

elm/gigasecond/src/Gigasecond.elm

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+module Gigasecond exposing (add)
+
+import Time
+
+
+
+-- Add a gigasecond 10^9 (1,000,000,000) seconds
+
+
+add : Time.Posix -> Time.Posix
+add timestamp =
+    Time.millisToPosix (Time.posixToMillis timestamp + gigasecond)
+
+
+gigasecond : Int
+gigasecond =
+    10 ^ 12

elm/gigasecond/tests/Tests.elm

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+module Tests exposing (tests)
+
+import Expect
+import Gigasecond exposing (add)
+import Iso8601
+import Parser
+import Test exposing (..)
+import Time
+
+
+tests : Test
+tests =
+    describe "Gigasecond"
+        [ describe "add"
+            [ test "2011-04-25" <|
+                \() ->
+                    Expect.equal "2043-01-01T01:46:40.000Z"
+                        (gigasecond "2011-04-25")
+            , test "1977-06-13" <|
+                    \() ->
+                        Expect.equal "2009-02-19T01:46:40.000Z"
+                            (gigasecond "1977-06-13")
+            , test "1959-07-19" <|
+                    \() ->
+                        Expect.equal "1991-03-27T01:46:40.000Z"
+                            (gigasecond "1959-07-19")
+            , test "full time specified" <|
+                    \() ->
+                        Expect.equal "2046-10-02T23:46:40.000Z"
+                            (gigasecond "2015-01-24T22:00:00.000Z")
+            , test "full time with day roll-over" <|
+                    \() ->
+                        Expect.equal "2046-10-03T01:46:39.000Z"
+                            (gigasecond "2015-01-24T23:59:59.000Z")
+            ]
+        ]
+
+
+gigasecond : String -> String
+gigasecond date =
+    case Iso8601.toTime date of
+        Ok posix ->
+            posix
+                |> Gigasecond.add
+                |> Iso8601.fromTime
+
+        _ ->
+            ""