Merge branch 'master' of https://github.com/Esri/arcgis-python-api

Merge pull request Esri#365 from DavidJVitale/insecure_url_nb

Added Insecure Notebook Sample

Adding v1.5.3 API doc so we can tag v1.5.3 samples and guides

Merge pull request Esri#332 from jyaistMap/v152-release-notes

Release notes for the upcoming v1.5.2. release

Merge pull request Esri#326 from DavidJVitale/master

Added 1.5.1 API doc to public repo for tagged release

Merge pull request Esri#298 from Esri/dev_site_current

Updated SDK for 8/30 website update

Merge pull request Esri#261 from DavidJVitale/master

thanks @DavidJVitale @jyaistMap

Merge pull request Esri#230 from DavidJVitale/master

Adding v1.4.1 API doc to master. Thank you @DavidJVitale

Merge pull request Esri#179 from jyaistMap/guide-install-sys-req

In interest of time, let us break out the Pro install pages for after DevSummit (March 2018)

SDK with updated guide, samples and ref doc for v1.3 of Python API (E…

…sri#164)