Create Crystal.gitignore

[keplersj]

Taken from the Crystal compiler's project init feature. Gitignore created by @flaviut.

What is it?

Crystal is a language derived from Ruby, compiled for the LLVM. Because it's only syntactically similar to Ruby there are some differences which should be taken into account.

What is being ignored?

Files created by the compiler in a normal session are being ignored here. .deps is where the compiler pulls in dependencies declared in a project's Projectfile. libs is similar is that it is external code downloaded later. .crystal is contains the LLVM bytecode created by the compiler at compilation. doc is well documentation. And .deps.lock is comparable to a Gemfile.lock.

Why?

Crystal is a fairly new language which has been recently gathering a following. Thought it would be nice for new Crystal projects on GitHub projects to be created with a proper gitignore.

[keplersj]

/cc @asterite @bcardiff @waj @jhass

[bcardiff]

👍 LGTM for the time being.
Things might change a little when dependency system get more mature towards 1.0.

Thanks @k2b6s9j

NB: The submitted .gitignore is consistent with the built in crystal init command which uses https://github.com/manastech/crystal/blob/master/src/compiler/crystal/tools/init/template/gitignore.ecr

[veelenga]

Since 0.8.0 release Crystal use shards to resolve dependencies and .gitignore need to be refreshed:

.deps -> .shards
.deps.lock -> shard.lock

[keplersj]

This PR has gone outdated and superseded by #2309. However, considering that this is my oldest sitting Pull Request at 2 years and 5 days it seems unlikely that GitHub will take in new language gitignores. 😒 That being said I've been using @joeblau's gitignore.io personally and it works great.