Connection, Stream: performance optimizations. Fixes #47
Flow: bind frequently used functions in advance.
Connection: minor improvements to the _send() method
Connection, Flow: don't call _send when it's not necessary
Compressor: fixing typo
Flow tests: fixing problem related to refactored _send() calls.
Connection: further reducing the number of invocations of _send()
Compressor: improvind code readability.
Flow: refactoring _push() since large part of its responsibilities are now in read()
Example server: small simplification.
README: shortening example code.
Flow: add missing semicolon.
Stream: don't use events for internal control flow.
Flow: removing 'sending' and 'receiving' events. Control flow now does not rely on them.
Connection: maintaining free stream slot count instead of used stream count.
Flow: save some unnecessary unshifts.
Connection, Stream: storing stream ID in the stream object.
All: always turning on assertions since it has practically zero performance penalty
All: making stream and flags property on frames necessary
HTTP: simplifying check of mandatory header fields.