replace stringbuffer with string builder for multicore performance
Update migrator.html

Fix spelling.
add link to article [Simplifying the distinction between SL4J and commons logging]
added note to point out reason for using string builder
Merge pull request #52 from vivekpathak/vpathak_stringbuilder_for_better_multicore_formatter

Use string builder instead of StringBuffer when builder is not shared. this avoids unnecessary lock spinning in the JVM.
Merge pull request #49 from motlin/master

Fix typo.
Merge pull request #48 from larrys/patch-1

Fixed spelling mistakes.
Fix typos.