CODEOFCONDUCT: add Homebrew CoC, diversity doc.

Add the Homebrew Code of Conduct and Diversity statement.

These are heavily based on those created by Python:
http://www.python.org/psf/codeofconduct/
http://www.python.org/community/diversity/

Closes Homebrew/legacy-homebrew#26904.

.gitignore

@@ -1,6 +1,7 @@
 /*
 !/.gitignore
 !/Library/
+!/CODEOFCONDUCT.md
 !/CONTRIBUTING.md
 !/README.md
 !/SUPPORTERS.md

CODEOFCONDUCT.md

@@ -0,0 +1,25 @@
+# Code of Conduct
+The Homebrew community is made up of members from around the globe with a diverse set of skills, personalities, and experiences. It is through these differences that our community experiences great successes and continued growth. When you're working with members of the community, we encourage you to follow these guidelines which help steer our interactions and strive to keep Homebrew a positive, successful, and growing community.
+
+A member of the Homebrew community is:
+
+## Open
+Members of the community are open to collaboration, whether it's on GitHub, email, IRC or otherwise. We're receptive to constructive comment and criticism, as the experiences and skill sets of other members contribute to the whole of our efforts. We're accepting of all who wish to take part in our activities, fostering an environment where anyone can participate and everyone can make a difference.
+
+## Considerate
+Members of the community are considerate of their peers - other Homebrew users. We're thoughtful when addressing the efforts of others, keeping in mind that often times the labor was completed simply for the good of the community. We're attentive in our communications, whether in person or online, and we're tactful when approaching differing views.
+
+## Respectful
+Members of the community are respectful. We're respectful of others, their positions, their skills, their commitments, and their efforts. We're respectful of the volunteer efforts that permeate the Homebrew community. We're respectful of the processes set forth in the community, and we work within them. When we disagree, we are courteous in raising our issues.
+
+Overall, we're good to each other. We contribute to this community not because we have to, but because we want to. If we remember that, these guidelines will come naturally.
+
+# Diversity
+The Homebrew community welcomes and encourages participation by everyone. Our community is based on mutual respect, tolerance, and encouragement, and we are working to help each other live up to these principles. We want our community to be more diverse: whoever you are, and whatever your background, we welcome you.
+
+We have created this diversity statement because we believe that a diverse Homebrew community is stronger and more vibrant. A diverse community where people treat each other with respect has more potential contributors and more sources for ideas.
+
+Although we have phrased the formal diversity statement generically to make it all-inclusive, we recognize that there are specific attributes that are used to discriminate against people. In alphabetical order, some of these attributes include (but are not limited to): age, culture, ethnicity, gender identity or expression, national origin, physical or mental difference, politics, race, religion, sex, sexual orientation, socio-economic status, and subculture. We welcome people regardless of the values of these or other attributes.
+
+# Attribution
+This code of conduct is heavily based on the [Python Community Code of Conduct](http://www.python.org/psf/codeofconduct/) and the [Python Diversity Statement](http://www.python.org/community/diversity/).

CONTRIBUTING.md

@@ -13,6 +13,7 @@ Contributing
 ------------
 Please read:
 
+* [Code of Conduct](https://github.com/Homebrew/homebrew/blob/master/CODEOFCONDUCT.md)
 * [Formula Cookbook](https://github.com/Homebrew/homebrew/wiki/Formula-Cookbook)
 * [Acceptable Formulae](https://github.com/Homebrew/homebrew/wiki/Acceptable-Formulae)
 * [Ruby Style Guide](https://github.com/styleguide/ruby)