My friends and I made a tool called Gleek.io that you can use to create all kinds of software diagrams from the text (UML class, sequence, ER diagrams, flowcharts, software architecture, and more). Feedback welcome.

Go to www.gleek.io and click on "Create diagram"

Example to try:

Type "Shape1–>Shape2" for your first diagram

Happy to hear your feedback and answer your questions
We are building this tool for the software development community.