Huge release! Some deep refactors to improve reliability & speed plus the implementation of our new API specification

Added

• Add a helpful 404 page during development that lists the page you might have wanted @KyleAMathews
  to link to or how to create a new page at that link #1051 @KyleAMathews
• Add "Plop" script for quickly creating new packages #1059 @KyleAMathews
• Add new plugin supporting server rendering of Styled Components #1060 @gutenye
• Add new plugin supporting server rendering of react-helmet #1085 @KyleAMathews
• Add new plugin for extracting JSDocs information from JavaScript files using documentation.js #1053 @KyleAMathews
• Add new API spec (rough draft) @KyleAMathews https://www.gatsbyjs.org/docs/api-specification/
• Add new API reference pages @KyleAMathews e.g. https://www.gatsbyjs.org/docs/node-apis/
• Add "duotone" image processing option to gatsby-plugin-sharp #1047 @fk
• Add example site for image processing @fk https://image-processing.gatsbyjs.org/
• Add example site for css-in-js library Glamor @KyleAMathews https://using-glamor.gatsbyjs.org/
• Add example site for css-in-js library Styled Components @KyleAMathews https://using-styled-components.gatsbyjs.org/

Changed

Grand big API renaming based on our new API spec https://www.gatsbyjs.org/docs/api-specification/

API changes:

Action creators:

• upsertPage is now createPage
• addFieldToNode is now createNodeField
• deletePageByPath is now deletePage
• addNodeToParent is now createParentChildLink

gatsby-browser.js APIs:

• clientEntry is now onClientEntry

gatsby-node.js APIs:

• onNodeCreate is now onCreateNode
• onUpsertPage is now onCreatePage
• extendNodeType is now setFieldsOnGraphQLNodeType

gatsby-ssr.js APIs:

• modifyHeadComponents and modifyPostBodyComponents were removed in favor of a
  new API onRenderBody.
• replaceServerBodyRender is now replaceRenderer

Fixed

• Fix sharp image quality and force file format (#1054) @0x80
• Expose crop focus parameter and make consistent with base64 #1055 @0x80
• Clean up TravisCI config #1066 @hawkrives
• Fix inference bug #1087 @jquense
• Provide default context for GraphQL #1052 @KyleAMathews
• Make determining when a given stage is finished much more reliable #1080 @KyleAMathews
• Pick values off plugin's package.json to avoid weird metadata from NPM #1090 @KyleAMathews

New 1.0 sites launched

• https://www.vauxlab.com
• https://meetfabric.com