Add integration amplitude (#61)

This commit copies the content of the integration repo into
the "integrations" folder.

Original repo: https://github.com/segment-integrations/analytics.js-integration-amplitude
Readme: https://github.com/segment-integrations/analytics.js-integration-amplitude/blob/master/README.md

Author: ccnixon

integrations/amplitude/HISTORY.md

@@ -0,0 +1,146 @@
+2.8.0 / 2018-04-04
+==================
+
+  * Update SDK version to 4.1.1
+
+2.7.0 / 2018-02-12
+==================
+
+  * anonymousID-as-deviceID + group{Type, Value}Trait support (#38)
+
+2.6.0 / 2017-09-18
+==================
+
+  * Update Amplitude to 3.7.0
+
+2.5.0 / 2017-08-30
+==================
+
+  * Improve revenue tracking from Order Completed events.
+
+2.4.0 / 2017-05-17
+==================
+
+  * Patch potential duplicate track event issue when using Groups functionality.
+
+2.4.0 / 2017-05-17
+==================
+
+  * Add support for Amplitude's `group` functionality to both identify and track events
+
+2.3.0 / 2017-04-11
+==================
+
+  * Allow mapping query params from context.page.search to a custom user/event property
+
+2.2.0 / 2016-11-15
+==================
+
+  * Update Amplitude v3.4.0 with support for forceHttps, trackGclid, saveParamsReferrerOncePerSession, deviceIdFromUrlParam options.
+
+2.1.1 / 2016-08-08
+==================
+
+  * Only send revenue event if revenue is being tracked
+
+2.1.0 / 2016-07-21
+==================
+
+  * update amplitude v3.0.2 with support for logrevenueV2 option
+  * Update Karma to 1.1.0
+
+2.0.0 / 2016-06-21
+==================
+
+  * Remove Duo compatibility
+  * Add CI setup (coverage, linting, cross-browser compatibility, etc.)
+  * Update eslint configuration
+
+1.0.16 / 2016-05-07
+==================
+
+  * Bump Analytics.js core, tester, integration to use Facade 2.x
+
+1.0.15 / 2016-05-02
+===================
+
+  * correctly set options
+
+1.0.14 / 2016-03-16
+===================
+
+  * Update Amplitude v2.9.1
+  * Fix bug where saveReferrer throws exception if sessionStorage is disabled.
+  * Log messages with a try/catch to support IE 8.
+  * Validate event properties during logEvent and initialization before sending request.
+  * Add instructions for proper integration with RequireJS.
+
+1.0.13 / 2016-02-11
+===================
+
+  * Updating Amplitude SDK v2.9.0
+
+1.0.12 / 2016-01-11
+===================
+
+  * Merge pull request #11 from amplitude/fix-runqueuedfunctions
+  * Only runQueuedFunctions after SDK loads
+1.0.11 / 2015-12-04
+===================
+
+  * updating Amplitude SDK v2.7.0
+
+1.0.10 / 2015-11-07
+===================
+
+  * updating Amplitude SDK v2.6.1
+
+1.0.9 / 2015-11-03
+==================
+
+  * updating amplitude SDK v2.6.0
+
+1.0.8 / 2015-10-21
+==================
+
+  * updating Amplitude SDK to v2.5.0
+
+1.0.7 / 2015-09-23
+==================
+
+  * Update Amplitude javascript sdk to v2.4.1
+
+1.0.6 / 2015-09-23
+==================
+
+  * Update Amplitude javascript sdk to v2.3.0
+
+1.0.5 / 2015-08-26
+==================
+
+  * Update Amplitude version to 2.2.1
+
+1.0.4 / 2015-06-30
+==================
+
+  * Replace analytics.js dependency with analytics.js-core
+
+1.0.3 / 2015-06-30
+==================
+
+  * Replace analytics.js dependency with analytics.js-core
+
+1.0.2 / 2015-06-24
+==================
+
+  * Bump analytics.js-integration version
+
+1.0.1 / 2015-06-24
+==================
+
+  * Bump analytics.js-integration version
+
+1.0.0 / 2015-06-09
+==================
+
+  * Initial commit :sparkles:

integrations/amplitude/README.md

@@ -0,0 +1,12 @@
+# analytics.js-integration-amplitude [![Build Status][ci-badge]][ci-link]
+
+Amplitude integration for [Analytics.js][].
+
+## License
+
+Released under the [MIT license](LICENSE).
+
+
+[Analytics.js]: https://segment.com/docs/libraries/analytics.js/
+[ci-link]: https://circleci.com/gh/segment-integrations/analytics.js-integration-amplitude
+[ci-badge]: https://circleci.com/gh/segment-integrations/analytics.js-integration-amplitude.svg?style=svg