Adding contributing guidelines and update README

Author: gusamarante

CONTRIBUTING.md

@@ -0,0 +1,13 @@
+# Contributing
+
+When contributing to this repository, please first discuss the change you wish 
+to make via issue or pull request. Make sure that any contributions use 
+consistent code conventions and clear function/method/variable names. The code 
+must be clearly commented, documenting intentions and edge cases. There must be 
+no sensitive materials in the revision history, issues, or pull requests (for 
+example, passwords or other non-public information).
+
+Please be polite and cordial in your interactions.
+
+If you need more information and help, specially about contributing, you can 
+contact Gustavo Amarante on [email protected]

README.md

@@ -1,4 +1,22 @@
+[paper_website]: https://www.newyorkfed.org/medialibrary/media/research/staff_reports/sr340.pdf
+[inference_atribute]: https://github.com/gusamarante/pyacm/blob/ba641c14e450fc83d22db4ef5e60eadbd489b351/pyacm/acm.py#L203
+**Still under development...**
+
 # pyacm
-Implementation of "Pricing the Term Structure with Linear Regressions" from Adrian, Crump and Moench (2013)
+Implementation of ["Pricing the Term Structure with Linear Regressions" from 
+Adrian, Crump and Moench (2013)][paper_website].
+
+The `NominalACM` class prices the time series and cross-section of the term 
+structure of interest rates using a three-step linear regression approach.
+Computations are fast, even with a large number of pricing factors. The object 
+carries all the relevant measures as atributes:
+- SOON...
+
+# Example
+SOON...
+
 
-Still under development...
+### Observations
+I am not completely sure that computations in the [inferences attributes]
+[inference_atribute] are correct. If you find any mistakes, please open a pull 
+request following the contributing guidelines.