Scanner token parsing refactor

[nfrasser]

The DOMAIN token (among others) has been removed in favour of WORD, UWORD and other tokens. SCHEME (formerly PROTOCOL) tokens now come in several flavours.

Includes additional facilities for token groups, which will be useful for future plugins down the line.

Removes some invalid mentions which probably never should have been marked as mentions

Fixes #171
Fixes #245
Fixes #351

[coveralls]

Pull Request Test Coverage Report for Build 1327368545

• 292 of 297 (98.32%) changed or added relevant lines in 10 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+92.7%) to 92.732%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/linkifyjs/src/linkify.js	2	7	28.57%

Totals
Change from base Build 1246226134:	92.7%
Covered Lines:	844
Relevant Lines:	878

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 1327368545

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 292 of 297 (98.32%) changed or added relevant lines in 10 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.2%) to 92.812%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/linkifyjs/src/linkify.js	2	7	28.57%

Totals
Change from base Build 1246226134:	-0.2%
Covered Lines:	844
Relevant Lines:	878

---

💛 - Coveralls