Checks that the `error` field is really and `error` type.
Merge pull request #40 from aybabtme/assert-type-avoid-panics

Checks that the `error` field is really of `error` type.
Export package func to a standard logger.
Add readme paragraph about package exported funcs.
Fix missing var args expansion.
readme: backwards compatibility notice
Merge pull request #45 from aybabtme/export-package-level-log-funcs

Export package func to a standard logger.
levels: add string helper
entry: use level string helper
entry: break out time, level and message from data
entry: document entry and methods
readme: document log rotation
formatter: drop internalFormatter
readme: fix levels
Merge pull request #48 from Sirupsen/break-out-specials

entry: break out time, level and message from data
readme: encourage package level logging

Conflicts:
	README.md
readme: fix examples
exported: export to be api compatible