use pkg supplied license file

Author: bpostlethwaite

LICENSE

@@ -0,0 +1,26 @@
+The Plotly.jl package is licensed under the MIT "Expat" License:
+
+> Copyright (c) 2015:
+>  * Shilei Zheng
+>  * Leah Hanson
+>  * Bryan A. Knowles
+>  * chriddyp
+>
+> Permission is hereby granted, free of charge, to any person obtaining
+> a copy of this software and associated documentation files (the
+> "Software"), to deal in the Software without restriction, including
+> without limitation the rights to use, copy, modify, merge, publish,
+> distribute, sublicense, and/or sell copies of the Software, and to
+> permit persons to whom the Software is furnished to do so, subject to
+> the following conditions:
+>
+> The above copyright notice and this permission notice shall be
+> included in all copies or substantial portions of the Software.
+>
+> THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+> EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+> MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+> IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+> CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+> TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+> SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.