Correct misspelling
Merge pull request #342 from chivalry/master

Correct spelling error.
Merge pull request #340 from cwahbong/test-fix

Never rely on waiting for Vim to finish something, instead make it write a file.
Refactor: split test.py into several smaller files.
Test refactorings.
Implement priority-based clearsnippets.
Code cleanup.

Full tested and does not break and old tests.
Refactor: snippet dictionary does not keep the extend info now.