sieve: create and validate starter implementation

twelve-days: create and validate starter implementation

Move contributing info into CONTRIBUTING file and add mention of rebases

spiral-matrix: add to track

complex-numbers: add to track

Standardize order of test annotations

Create RESOURCES.md and add resources

Clean up exception-related hints

Formatted Stack Overflow with a space in between.
Capitalized Java in the Reddit link and removed the claim that it was official.
Removed Gitter room link
The documentation is official

journey test: fix for trackler submodule rename

https://github.com/exercism/trackler/commit/69e055ad52b3f8d19da95b6ab0593678b8ee1bb4

list-ops: estimate difficulty 9

poker : add to track

bank-account: add to track

hamming: update to v1.1.0 of canonical data

https://github.com/exercism/problem-specifications/blob/ebe9bbf952206384d344aded650407751a881e92/exercises/hamming/canonical-data.json

Updates now that two-fer is part of the track!

See
https://github.com/exercism/docs/blob/fe38450da526a35368e98fdb2f83ca40f1298aee/contributing-to-language-tracks/README.md#adding-hints

pangram: update to 1.1.0

JAVA -> Java

Java is not an acronym or an abbreviation, it should not be written in all-caps (doing so encourages the misunderstanding further, especially as exerscism.io is aimed at newbies!).

two-fer: add to track