fixed documentation bug as per issue #4029
Add _eval_nseries method for expint()
Some tests for expint series
Merge pull request #2495 from perseus0807/4029_iterables

fixed documentation bug as per issue #4029
Add Vinit Ravishankar to AUTHORS/aboutus. Welcome to SymPy!
Merge pull request #2511 from smichr/auth

Add Vinit Ravishankar to AUTHORS/aboutus. Welcome to SymPy!
Merge pull request #2505 from skirpichev/2958-series-for-error_functions.py

Implement missing series methods for exponential integrals (first part of the issue 2958)
Doc changes
Rectified errors in docs