katex 0.6.0

v0.6.0 - aligned, \gt, \lt, \underline, and infrastructure work

on Node.js NPM

New features:

• Introduce the aligned environment.
• Add \gt and \lt.
• Bundle CSS and fonts in npm package.
• Fix sub- and super-scripts not being centered inside of math display.
• Add \underline support.

Other changes:

• Remove 3px border around rules (bug fix).
• Set the greediness of font functions to 2 so that e^\mathbf{x} will parse (bug fix).

Infrastructure changes:

• Refactor function and symbol tables.
• Add calling convention for functions and environments.
• Make mode and position part of the internal state.
• Check screenshots on Travis using Docker and Selenium and changes to increase the robustness of these tests.
• Add unit tests for error messages.

Special thanks to @gagern for all of the infrastructure changes.