Update README.md

Added another benifit over ack.
Performance tweak: reduce number of function call of strlen()
Add check for EOF to prevent infinite loop

Fixes #299
Merge pull request #300 from lee-dohm/bug-299

Add check for EOF to prevent infinite loop
Merge pull request #297 from yongzhy/fea_strlen

Performance tweak: reduce number of function call of strlen()
Don't call lzma functions if we don't have lzma.h. This should fix #280.
Handle '-i' before '-g' or '-G' properly

'ag -i -g <filename_pattern>' should perform case insensitive filename
search

'ag -i -G <filename_pattern> <needle>' should perform case sensitive
search for needle in case insensitive filenames

'ag -G <filename_pattern> -i <needle>' should perform case insensitive
search for needle in case sensitive filenames

'ag -i -G <filename_pattern> -i <needle>' should be case insensitive for
both

Fix #302
Merge pull request #303 from mcphail/issue_302

Handle '-i' before '-g' or '-G' properly
Oops - should be using bitwise AND
Merge pull request #304 from mcphail/issue_302

Oops - should be using bitwise AND
More accurate build and install requirements

I found that, during the configure step, we're depending on
at least the presence of three packages above and beyond a
vanilla CentOS install and the development tools. I've
therefore omitted the development tools as well, as per
modern packaging guidelines. See https://fedoraproject.org/wiki/How_to_create_an_RPM_package#SPEC_file_overview
for more information.
Merge pull request #305 from emilyst/patch-1

More accurate build and install requirements
Merge pull request #296 from wvdschel/patch-1

Update README.md