Add documentation for disabling YARA rules

[austinbyers]

to: @ryandeivert cc: @airbnb/binaryalert-maintainers size: small

Background

Issue #95 brought some questions about fixing or removing YARA rules which aren't supported (e.g. with those with special modules).

Changes

• Adds a note to the documentation that we are working on a more expressive rule cloning
• Adds a section to the documentation on how to disable rules files or individual YARA rules

Testing

• sphinx-build -W docs/source docs/build and viewing built file locally

[coveralls]

Coverage remained the same at 92.787% when pulling d2e2ac2de1fea30a8d8abac6f6c9153bb1e051d5 on austin-disable-docs into b319e9fd1b0b814795e58a41acd2ebbe7814d105 on master.

[coveralls]

Coverage remained the same at 92.787% when pulling d2e2ac2de1fea30a8d8abac6f6c9153bb1e051d5 on austin-disable-docs into b319e9fd1b0b814795e58a41acd2ebbe7814d105 on master.