Merge pull request #2 from ChenShuang/master

ChenShuang: num_of_bits/num_of_words typo fix
Replaced loop with memset
Updated README; Added _alloc()/dealloc(); tidied up internal method names

Updated README
Added bit_array_alloc() bit_array_dealloc()
Faster creation of large arrays
Renamed internal functions to _name()
Fix error from Apple LLVM 4.2 compiler

Use of undeclared identifier 'bitarr'
Use of undeclared identifier 'start'
Merge pull request #3 from duhovny/master

Fix error from Apple LLVM 4.2 compiler: remove space between macro name and brackets
Removed explicit casts from double to float in test code