Better a11y rules for img-uses-alt

More descriptive error messaging for img-uses-alt
Allows alt="" when role="presentation" on img-uses-alt.

Handle list of roles for valid-aria-role.

Fixes #5

Handle null valued props for valid-aria-role.

Fixes #4

Implement valid-aria-role rule.

Based on https://github.com/GoogleChrome/accessibility-developer-tools/wiki/Audit-Rules#ax_aria_01

Handle LogicalExpression attribute type for getting value.

Fixes #2

Handle different node name types.

Fixes #1

Add no-hash-href rule

Enforces that href prop on element is not === '#'

Fixed TemplateLiteral AST value building.

Add redundant-alt rule

Implement redundant-alt rule which checks for redundancy in alt text.

Initial stable release

0.1.2

Specify linting directories.