Update README.md (practical-tutorials#141)

* Update README.md

Remove ambiguities in the introduction paragraph. Increase conciseness of sentences.

* Remove typos

README.md

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 # Project Based Learning
 [![Gitter](https://badges.gitter.im/practical-tutorials/community.svg)](https://gitter.im/practical-tutorials/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
 
-A list of programming tutorials in which learners build an application from scratch. These tutorials are divided into different primary programming languages. Some have intermixed technologies and languages.
+A list of programming tutorials in which aspiring software developers learn how to build an application from scratch. These tutorials are divided into different primary programming languages. Tutorials may involve multiple technologies and languages.
 
 To get started, simply fork this repo. Please refer to [CONTRIBUTING.md](CONTRIBUTING.md) for contribution guidelines.